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A322977
Number of even divisors d of n such that d-1 is prime.
6
0, 0, 0, 1, 0, 1, 0, 2, 0, 0, 0, 3, 0, 1, 0, 2, 0, 2, 0, 2, 0, 0, 0, 5, 0, 0, 0, 2, 0, 2, 0, 3, 0, 0, 0, 4, 0, 1, 0, 3, 0, 3, 0, 2, 0, 0, 0, 6, 0, 0, 0, 1, 0, 3, 0, 3, 0, 0, 0, 6, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 7, 0, 1, 0, 2, 0, 1, 0, 4, 0, 0, 0, 6, 0, 0, 0, 3, 0, 4, 0, 1, 0, 0, 0, 7, 0, 2, 0, 2, 0, 2, 0, 3, 0
OFFSET
1,8
COMMENTS
Equally: Number of divisors d of n such that d-1 is an odd prime.
FORMULA
a(n) = Sum_{d|n, d>1} A059841(d)*A010051(d-1).
a(n) <= A183063(n).
MATHEMATICA
Array[DivisorSum[#, 1 &, And[EvenQ@ #, PrimeQ[# - 1]] &] &, 105] (* Michael De Vlieger, Jan 04 2019 *)
PROG
(PARI) A322977(n) = sumdiv(n, d, (!(d%2))*isprime(d-1));
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jan 04 2019
STATUS
approved