A366607 Sum of the divisors of 4^n+1.

3, 6, 18, 84, 258, 1302, 4356, 20520, 65538, 351120, 1110276, 5048232, 17041416, 82623888, 284225796, 1494039792, 4301668356, 20788904016, 73234343952, 332019460560, 1103789883396, 5936210280000, 18679788287496, 84884999116320, 282937726148616

Offset

0,1

Links

Max Alekseyev, Table of n, a(n) for n = 0..561

Formula

a(n) = sigma(4^n+1) = A000203(A052539(n)).

a(n) = A069061(2*n). - Max Alekseyev, Jan 08 2024

Example

a(3)=84 because 4^3+1 has divisors {1, 5, 13, 65}.

Maple

a:=n->numtheory[sigma](4^n+1):
seq(a(n), n=0..100);

Mathematica

DivisorSigma[1, 4^Range[0, 30]+1] (* Paolo Xausa, Oct 14 2023 *)

Prog

(Python)
from sympy import divisor_sigma
def A366607(n): return divisor_sigma((1<<(n<<1))+1) # Chai Wah Wu, Oct 14 2023

Crossrefs

Cf. A000203, A052539, A057940, A274903, A366603, A366605, A366606, A366608, A366609.

Cf. A069061, A366578, A366617, A366629, A366638, A366657, A366666, A366668, A366689, A366715.

Sequence in context: A076510 A220816 A038060 * A345134 A135504 A307334

Adjacent sequences: A366604 A366605 A366606 * A366608 A366609 A366610

Keyword

nonn

Author

Sean A. Irvine, Oct 14 2023

Status

approved