OFFSET
1,1
LINKS
Ivan Neretin, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = n + 1 for number in A078762 (numbers n such that n + sigma(n) is prime).
EXAMPLE
For n = 6; a(n) = sigma(6 + sigma(6)) - sigma(6) = sigma(18) - sigma(6) = 39 - 12 = 27.
MATHEMATICA
sig[n_]:=Module[{d6=DivisorSigma[1, n]}, DivisorSigma[1, n+d6]-d6]; Array[ sig, 70] (* Harvey P. Dale, Feb 20 2015 *)
PROG
(Magma) [SumOfDivisors(n+SumOfDivisors(n))-SumOfDivisors(n):n in[1..1000]]
(PARI) vector(100, n, sigma(n+sigma(n))-sigma(n)) \\ Derek Orr, Sep 07 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Sep 07 2014
STATUS
approved