id:A147810 - OEIS Search Results

Search: id:A147810

Displaying 1-1 of 1 results found.

page 1

Half the number of divisors of n^2+1.

+0
4

1, 1, 2, 1, 2, 1, 3, 2, 2, 1, 2, 2, 4, 1, 2, 1, 4, 3, 2, 1, 4, 2, 4, 1, 2, 1, 4, 2, 2, 2, 4, 3, 4, 2, 2, 1, 4, 3, 2, 1, 3, 2, 6, 2, 2, 2, 8, 2, 2, 2, 2, 2, 4, 1, 4, 1, 8, 2, 2, 2, 2, 2, 4, 2, 2, 1, 4, 4, 2, 3, 2, 4, 8, 1, 4, 2, 4, 2, 2, 2, 4, 3, 8, 1, 2, 2, 4, 2, 4, 1, 4, 2, 6, 1, 2, 2, 4, 4, 6 (list; graph; listen)

	OFFSET	`1,3`
	COMMENT	`For any n>0, n^2+1 cannot be a square and thus has an even number of divisors which always include 1 and n^2+1, therefore a(n) is always a positive integer.`
	FORMULA	`a(n) = A000005(A002522(n))/2 = A147809(n)+1`
	PROGRAM	`(PARI) A147810(n)=numdiv(n^2+1)/2`
	CROSSREFS	`Cf. A048691.` `Sequence in context: A059829 A076558 A057217 this_sequence A055181 A073811 A125030` `Adjacent sequences: A147807 A147808 A147809 this_sequence A147811 A147812 A147813`
	KEYWORD	`easy,nonn`
	AUTHOR	`M. F. Hasler (MHasler(AT)univ-ag.fr), Dec 13 2008`

page 1

Search completed in 0.002 seconds

Last modified November 27 22:38 EST 2009. Contains 167602 sequences.

AT&T Labs Research