A155567 Intersection of A002479 and A020669 : N = a^2 + 2b^2 = c^2 + 5d^2 for some integers a,b,c,d.

0, 1, 4, 6, 9, 16, 24, 25, 36, 41, 49, 54, 64, 81, 86, 89, 96, 100, 121, 129, 134, 144, 150, 164, 166, 169, 196, 201, 214, 216, 225, 241, 246, 249, 256, 281, 289, 294, 321, 324, 326, 344, 356, 361, 369, 384, 400, 401, 409, 441, 449, 454, 484, 486, 489, 516, 521

Offset

1,3

Comments

Contains A155577 as a subsequence (obtained by restricting a,b,c,d to be nonzero). Also contains A000290 (squares) as subsequence.

Links

Table of n, a(n) for n=1..57.

Prog

(PARI) isA155567(n, /* use optional 2nd arg to get other analogous sequences */c=[5, 2]) = { for(i=1, #c, for(b=0, sqrtint(n\c[i]), issquare(n-c[i]*b^2) & next(2)); return); 1}
for( n=1, 600, isA155567(n) & print1(n", "))

Crossrefs

Cf. A001481, A002479, A003136, A002481, A020668 ff.

Sequence in context: A181018 A155569 A189484 * A225377 A036667 A371843

Adjacent sequences: A155564 A155565 A155566 * A155568 A155569 A155570

Keyword

easy,nonn

Author

M. F. Hasler, Jan 25 2009

Status

approved