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A155710 Intersection of A092572 and A154778: N = a^2 + 3b^2 = c^2 + 5d^2 for some positive integers a,b,c,d. 1
21, 36, 49, 61, 84, 109, 129, 144, 181, 189, 196, 201, 229, 241, 244, 301, 309, 324, 336, 349, 381, 409, 421, 436, 441, 469, 489, 516, 525, 541, 549, 576, 601, 661, 669, 709, 721, 724, 756, 769, 784, 804, 829, 849, 889, 900, 916, 921, 964, 976, 981, 1009, 1021 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Subsequence of A155570 (where a,b,c,d may be zero).

LINKS

Table of n, a(n) for n=1..53.

PROG

(PARI) isA155710(n, /* use optional 2nd arg to get other analogous sequences */c=[5, 3]) = { for(i=1, #c, for(b=1, sqrtint((n-1)\c[i]), issquare(n-c[i]*b^2) & next(2)); return); 1}

for( n=1, 1111, isA155710(n) & print1(n", "))

CROSSREFS

Cf. A000404, A154777, A092572, A097268, A154778, A155716, ...

Sequence in context: A219919 A219215 A342719 * A001491 A112352 A298472

Adjacent sequences:  A155707 A155708 A155709 * A155711 A155712 A155713

KEYWORD

easy,nonn

AUTHOR

M. F. Hasler, Jan 25 2009

STATUS

approved

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Last modified July 29 12:56 EDT 2021. Contains 346346 sequences. (Running on oeis4.)