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 A193432 Number of divisors of n^2 + 1. 20
 1, 2, 2, 4, 2, 4, 2, 6, 4, 4, 2, 4, 4, 8, 2, 4, 2, 8, 6, 4, 2, 8, 4, 8, 2, 4, 2, 8, 4, 4, 4, 8, 6, 8, 4, 4, 2, 8, 6, 4, 2, 6, 4, 12, 4, 4, 4, 16, 4, 4, 4, 4, 4, 8, 2, 8, 2, 16, 4, 4, 4, 4, 4, 8, 4, 4, 2, 8, 8, 4, 6, 4, 8, 16, 2, 8, 4, 8, 4, 4, 4, 8, 6, 16, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Seiichi Manyama, Table of n, a(n) for n = 0..10000 FORMULA a(n) = A000005(A002522(n)). - Michel Marcus, Mar 16 2018 EXAMPLE a(7) = 6 because 7^2+1 = 50 and the 6 divisors are { 1, 2, 5, 10, 25, 50}. MAPLE with(numtheory):for n from 0 to 110 do:n1:=nops(divisors(n^2+1)):s:=0:for m from 1 to n1 do: s:=s+1:od: printf(`%d, `, s):od: MATHEMATICA Array[DivisorSigma[0, #^2 + 1] &, 85, 0] (* Michael De Vlieger, Mar 17 2018 *) PROG (PARI) a(n) = numdiv(n^2+1); \\ Michel Marcus, Mar 16 2018 CROSSREFS Cf. A000005, A002522, A128428, A193330, A193433. Sequence in context: A147848 A306652 A239614 * A129089 A255201 A169594 Adjacent sequences:  A193429 A193430 A193431 * A193433 A193434 A193435 KEYWORD nonn AUTHOR Michel Lagneau, Jul 28 2011 STATUS approved

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Last modified July 28 23:26 EDT 2021. Contains 346340 sequences. (Running on oeis4.)