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A366578
Sum of the divisors of 3^n+1.
11
3, 7, 18, 56, 126, 434, 1332, 3836, 10476, 42560, 109926, 315112, 816732, 2790074, 8906760, 30220288, 64570086, 229156928, 706911048, 2034690952, 5357742012, 21838961760, 56496274632, 164750562956, 456919958880, 1517043139136, 4661686010664, 16489453890560
OFFSET
0,1
LINKS
FORMULA
a(n) = sigma(3^n+1) = A000203(A034472(n)).
EXAMPLE
a(4)=126 because 3^4+1 has divisors {1, 2, 41, 82}.
MAPLE
a:=n->numtheory[sigma](3^n+1):
seq(a(n), n=0..100);
MATHEMATICA
DivisorSigma[1, 3^Range[0, 30]+1] (* Paolo Xausa, Oct 15 2023 *)
KEYWORD
nonn
AUTHOR
Sean A. Irvine, Oct 13 2023
STATUS
approved