OFFSET
1,2
COMMENTS
n-th term = prime when n is prime.
This sequence is used in A131492 as an auxiliary sequence. - Reinhard Zumkeller, Feb 17 2012
LINKS
Enrique Pérez Herrero, Table of n, a(n) for n = 1..5000
W. D. Banks and F. Luca, On integers with a special divisibility property, Archivum Mathematicum (BRNO) 42 (2006) pp 31-42.
FORMULA
a(n) = Sum_{d|n} A002322(d).
EXAMPLE
a(6) = 6 = (1, 1, 1, 0, 0, 1) dot (1, 1, 2, 2, 4, 2) = (1 + 1 + 2 + 0 + 0 + 2); where (1, 1, 1, 0, 0, 1) = row 6 of triangle A051731.
MATHEMATICA
A141258[n_] := DivisorSum[n, CarmichaelLambda[#]&];
Table[A141258[n], {n, 1, 20}] (* Enrique Pérez Herrero, Apr 22 2014 *)
PROG
(PARI) a(n) = sumdiv(n, d, lcm(znstar(d)[2])); \\ see PARI script in A002322; Michel Marcus, Apr 22 2014
(Haskell)
a141258 = sum . map a002322 . a027750_row
-- Reinhard Zumkeller, Sep 02 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Gary W. Adamson, Jun 18 2008
EXTENSIONS
More terms from R. J. Mathar, Jan 19 2009
STATUS
approved