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 A261609 Number of composite divisors of n^2+1. 1
 0, 0, 1, 0, 1, 0, 3, 1, 1, 0, 1, 1, 4, 0, 1, 0, 4, 3, 1, 0, 4, 1, 4, 0, 1, 0, 4, 1, 1, 1, 4, 3, 4, 1, 1, 0, 4, 3, 1, 0, 3, 1, 8, 1, 1, 1, 11, 1, 1, 1, 1, 1, 4, 0, 4, 0, 12, 1, 1, 1, 1, 1, 4, 1, 1, 0, 4, 5, 1, 3, 1, 4, 11, 0, 4, 1, 4, 1, 1, 1, 4, 3, 11, 0, 1, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,7 LINKS Michel Lagneau, Table of n, a(n) for n = 1..10000 FORMULA a(n) = A055212(A002522(n)). EXAMPLE a(7) = 3 because the composite divisors of 7^2+1 are 10, 25, 50. MATHEMATICA Table[ Count[ PrimeQ[ Divisors[n^2+1] ], False] - 1, {n, 1, 105} ] CROSSREFS Cf. A002522, A055212, A128428, A193330, A193432. Sequence in context: A193140 A319993 A122776 * A228488 A338638 A062172 Adjacent sequences:  A261606 A261607 A261608 * A261610 A261611 A261612 KEYWORD nonn,easy AUTHOR Michel Lagneau, Aug 26 2015 STATUS approved

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Last modified June 21 10:09 EDT 2021. Contains 345360 sequences. (Running on oeis4.)