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Sum of divisors of 2*prime(n)+1.
4

%I #15 Apr 26 2024 03:15:15

%S 6,8,12,24,24,40,48,56,48,60,104,124,84,120,120,108,144,168,240,168,

%T 228,216,168,180,336,240,312,264,296,228,432,264,372,416,336,408,624,

%U 440,408,348,360,532,384,572,480,640,624,600,672,720,468

%N Sum of divisors of 2*prime(n)+1.

%H Reinhard Zumkeller, <a href="/A072057/b072057.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A000203(A072055(n)).

%e Divisors of A072055(8) = 2*A000040(8)+1 = 2*19+1 = 39: {1,3,13,39}, therefore a(8) = 1+3+13+39 = 56.

%t DivisorSigma[1,#]&/@(2Prime[Range[60]]+1) (* _Harvey P. Dale_, Sep 17 2013 *)

%o (Haskell)

%o a072057 = a000203 . a072055 -- _Reinhard Zumkeller_, Oct 10 2013

%o (PARI) a(n) = sigma(2*prime(n)+1); \\ _Amiram Eldar_, Apr 26 2024

%o (PARI) lista(pmax) = forprime(p = 2, pmax, print1(sigma(2*p+1), ", ")); \\ _Amiram Eldar_, Apr 26 2024

%Y Cf. A000040, A000203, A072055, A072056.

%K nonn

%O 1,1

%A _Reinhard Zumkeller_, Jun 11 2002