OFFSET
1,2
COMMENTS
a(n) = prime(n) if n is prime but nonprime n's can also have prime a(n).
Equals left border of triangle A158902.
FORMULA
A051731 * [1, 1, 2, 3, 4, 5, ...] = inverse Mobius transform of [1, 1, 2, 3, 4, ...].
a(n) = sigma(n) - d(n) + 1. - Juri-Stepan Gerasimov, Aug 30 2009
a(n) = 1 + A065608(n). - R. J. Mathar, Jan 08 2015
EXAMPLE
a(4) = 5 = (1, 1, 0, 1) dot (1, 1, 2, 3) = (1 + 1 + 0 + 3); where (1, 1, 0, 1) = row 4 of triangle A051731.
MAPLE
L := [1, seq(n, n=1..100)] ; read("transforms"); MOBIUSi(L) ; # R. J. Mathar, Apr 02 2009
PROG
(PARI) a(n) = sigma(n) - numdiv(n) + 1; \\ Michel Marcus, Sep 14 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Gary W. Adamson, Mar 29 2009
STATUS
approved