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A193562 Number of divisors of n^4+1. 2
1, 2, 2, 4, 2, 4, 2, 4, 4, 8, 4, 4, 4, 4, 4, 8, 2, 4, 4, 8, 2, 4, 4, 4, 2, 8, 4, 8, 2, 4, 4, 8, 4, 8, 2, 4, 4, 8, 4, 4, 4, 8, 4, 16, 8, 8, 2, 8, 2, 8, 4, 8, 4, 8, 2, 8, 2, 4, 4, 16, 8, 4, 4, 8, 8, 4, 8, 8, 4, 8, 8, 4, 4, 4, 2, 8, 8, 16, 4, 16, 2, 4, 2, 16, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

This is to n^4+1 as A193432 is to n^2+1. a(n) = 2 when n^4+1 is prime, iff n is in A037896.

LINKS

Table of n, a(n) for n=0..84.

FORMULA

a(n) = A000005(A002523(n)) = d(n^4+1) (also called tau(n^4+1) or sigma_0(n^4+1)), the number of divisors of n^4+1.

EXAMPLE

a(3) = 4 because 3^4+1 = 82, whose 4 factors are {1, 2, 41, 82}.

MATHEMATICA

DivisorSigma[0, Range[0, 90]^4+1] (* Harvey P. Dale, May 05 2013 *)

CROSSREFS

Cf. A000005, A002523, A037896, A193432 (number of divisors of n^2+1).

Sequence in context: A106469 A082508 A303809 * A249868 A255311 A075526

Adjacent sequences:  A193559 A193560 A193561 * A193563 A193564 A193565

KEYWORD

nonn,easy

AUTHOR

Jonathan Vos Post, Aug 09 2011

STATUS

approved

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Last modified January 18 07:18 EST 2019. Contains 319269 sequences. (Running on oeis4.)