A204998 a(n) = k^2 - j^2, where (k^2,j^2) is the least pair of distinct squares for which n divides their difference.

3, 8, 3, 8, 5, 12, 7, 8, 9, 20, 11, 12, 13, 28, 15, 16, 17, 72, 19, 20, 21, 44, 23, 24, 75, 52, 27, 28, 29, 60, 31, 32, 33, 68, 35, 72, 37, 76, 39, 40, 41, 84, 43, 44, 45, 92, 47, 48, 147, 200, 51, 52, 53, 108, 55, 56, 57, 116, 59, 60, 61, 124, 63, 64, 65, 132, 67, 68, 69, 140, 71, 72, 73, 148, 75, 76, 77, 156, 79, 80, 81, 164

Offset: 1

Author

Clark Kimberling, Jan 21 2012

Keywords

• nonn

Comments

For a guide to related sequences, see A204892.

Links

• Antti Karttunen, Table of n, a(n) for n = 1..23005

Crossrefs

Cf. A204994, A204892, A204996, A204997, A204999.

Programs

Mathematica

(See the program at A204994.)

PARI

A204998(n) = { my(d); for(k=sqrtint(1+n), oo, for(j=1,k-1,if(!((d=(k^2)-(j^2))%n),return(d),if(dAntti Karttunen, Sep 28 2018

Formula

a(n) = A204996(n) - A204997(n).

Extensions

More terms from Antti Karttunen, Sep 28 2018