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A161116 a(n) is the number of nontrivial positive divisors of 2n+3. 1
0, 0, 0, 1, 0, 0, 2, 0, 0, 2, 0, 1, 2, 0, 0, 2, 2, 0, 2, 0, 0, 4, 0, 1, 2, 0, 2, 2, 0, 0, 4, 2, 0, 2, 0, 0, 4, 2, 0, 3, 0, 2, 2, 0, 2, 2, 2, 0, 4, 0, 0, 6, 0, 0, 2, 0, 2, 4, 2, 1, 2, 2, 0, 2, 0, 2, 6, 0, 0, 2, 2, 2, 4, 0, 0, 4, 2, 0, 2, 2, 0, 6, 0, 1, 4, 0, 4, 2, 0, 0, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,7

COMMENTS

a(n)=0 iff n is in A067076, i.e., 2n+3 is prime; a(n) is the number of positive integers of the form (n-3k)/(2k+1), 1<=k<=n/3.

LINKS

Table of n, a(n) for n=0..90.

FORMULA

For n>=1, a(n)=A160973(n)+A079978(n). [Vladimir Shevelev, Jun 07 2009]

a(n) = A070824(2n+3).

EXAMPLE

Since for n=3 we have 2n+3=9 and only nontrivial divisor of 9 is 3, then a(3)=1.

PROG

(PARI) a(n) = numdiv(2*n+3) - 2; \\ Michel Marcus, Feb 08 2016

(MAGMA) [NumberOfDivisors(2*n+3)-2: n in [0..100]]; // Vincenzo Librandi, Feb 08 2016

CROSSREFS

Cf. A067076, A034953, A054269, A082749, A006254.

Cf. A160973. - Vladimir Shevelev, Jun 07 2009

Sequence in context: A324730 A118683 A175800 * A262726 A112605 A111775

Adjacent sequences:  A161113 A161114 A161115 * A161117 A161118 A161119

KEYWORD

nonn,easy

AUTHOR

Vladimir Shevelev, Jun 02 2009

EXTENSIONS

Edited by Charles R Greathouse IV, Oct 12 2009

More terms from Michel Marcus, Feb 08 2016

STATUS

approved

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Last modified November 12 14:35 EST 2019. Contains 329058 sequences. (Running on oeis4.)