find palindromic U-shaped triangular arrays in OEIS; see https://math.stackexchange.com/questions/4835012

OEISScanner.java

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.math.BigInteger;

public class OEISScanner {
    public static void main (String [] args) throws IOException {
        // OEIS sequence data downloaded from https://oeis.org/stripped.gz
        BufferedReader reader = new BufferedReader (new FileReader (args [0]));
        
        outer:
        for (;;) {
            String line = reader.readLine();
            if (line == null)
                break;
            if (line.startsWith("#"))
                continue;
            int space = line.indexOf(' ');
            String name = line.substring(0,space);
            String [] terms = line.substring(space + 2).split(",");
            
            boolean changed = false;
            
            for (int n = 1,i = 0;;n++) {
                int next = i + n;
                if (next > terms.length)
                    break;
                BigInteger last = null;
                for (int j = 0;j <= n - j - 1;j++) {
                    if (!terms [i + j].equals(terms [i + n - j - 1]))
                        continue outer;
                    try {
                        BigInteger value = new BigInteger (terms [i + j]).abs();
                        if (j != 0) {
                            if (value.compareTo(last) > 0)
                                continue outer;
                            if (!value.equals(last))
                                changed = true;
                        }
                        last = value;
                    } catch (NumberFormatException nfe) {
                        continue outer;
                    }
                }
                i = next;
            }

            if (changed)
                System.out.println("[" + name + "](https://oeis.org/" + name + ")");
        }
    }
}