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A155717
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Numbers of the form N = a^2 + 7b^2 for some positive integers a,b.
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11
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8, 11, 16, 23, 29, 32, 37, 43, 44, 53, 56, 64, 67, 71, 72, 77, 79, 88, 92, 99, 107, 109, 112, 113, 116, 121, 127, 128, 137, 144, 148, 149, 151, 161, 163, 172, 176, 179, 184, 191, 193, 197, 200, 203, 207, 211, 212, 224, 232, 233, 239, 253, 256, 259, 261, 263, 268
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OFFSET
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1,1
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COMMENTS
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Subsequence of A020670 (which allows for a and b to be zero).
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LINKS
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Table of n, a(n) for n=1..57.
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PROG
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(PARI) isA155717(n, /* optional 2nd arg allows us to get other sequences */c=7) = { for(b=1, sqrtint((n-1)\c), issquare(n-c*b^2) & return(1))}
for( n=1, 300, isA155717(n) & print1(n", "))
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CROSSREFS
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Cf. A000404, A154777, A092572, A097268, A154778, A155707-A155716, A155560-A155578.
Sequence in context: A154685 A068591 A065348 * A188197 A111254 A127271
Adjacent sequences: A155714 A155715 A155716 * A155718 A155719 A155720
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KEYWORD
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easy,nonn
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AUTHOR
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M. F. Hasler, Jan 25 2009
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STATUS
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approved
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