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Search: id:A155578
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| A155578 |
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Intersection of A000404 and A155717: N = a^2 + b^2 = c^2 + 7d^2 for some positive integers a,b,c,d. |
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+0
15
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| 8, 29, 32, 37, 53, 72, 109, 113, 116, 128, 137, 148, 149, 193, 197, 200, 212, 232, 233, 261, 277, 281, 288, 296, 317, 333, 337, 373, 389, 392, 400, 401, 421, 424, 436, 449, 452, 457, 464, 477, 512, 541, 548, 557, 569, 592, 596, 613, 617, 641, 648, 653, 673
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Subsequence of A155568 (where a,b,c,d may be zero).
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PROGRAM
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(PARI) isA155578(n, /* optional 2nd arg allows us to get other sequences */c=[7, 1]) = { 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, 999, isA155578(n) & print1(n", "))
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CROSSREFS
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Cf. A000404, A154777, A092572, A097268, A154778, A155716, ...
Sequence in context: A152014 A146977 A068623 this_sequence A115107 A035339 A034167
Adjacent sequences: A155575 A155576 A155577 this_sequence A155579 A155580 A155581
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KEYWORD
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easy,nonn
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AUTHOR
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M. F. Hasler (MHasler(AT)univ-ag.fr), Jan 25 2009
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