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A261558
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Euclid numbers (A006862) of the form 3*(i*i + i*j + j*j + i + j) + 1 where i and j are integers.
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0
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7, 31, 211, 2311, 510511, 6469693231, 200560490131, 304250263527211, 117288381359406970983271, 7858321551080267055879091, 40729680599249024150621323471, 232862364358497360900063316880507363071, 279734996817854936178276161872067809674997231
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OFFSET
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1,1
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COMMENTS
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LINKS
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EXAMPLE
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a(1) = 7 because 7 = 2*3 + 1 = 3*(1^2 + 1*0 + 0^2 + 1 + 0) + 1.
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PROG
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(PARI) a(n) = prod(k=1, n, prime(k)) + 1;
isA(n) = if( n<1 || (n%3 == 0), 0, 0 != sumdiv( n, d, kronecker( -3, d)));
for(n=0, 30, if(isA(a(n)), print1(a(n), ", ")))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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