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%I #24 Sep 08 2022 08:46:13
%S 2,10,17,50,37,145,65,226,170,325,145,785,197,577,577,962,325,1522,
%T 401,1765,1025,1297,577,3601,962,1765,1601,3137,901,5185,1025,3970,
%U 2305,2917,2305,8282,1445,3601,3137,8101,1765,9217,1937,7057,6085,5185,2305
%N a(n) = 1 + sigma(n)^2.
%H Robert Price, <a href="/A258974/b258974.txt">Table of n, a(n) for n = 1..10000</a>
%H OEIS Wiki, <a href="https://oeis.org/wiki/Cyclotomic Polynomials at x=n, n! and sigma(n)">Cyclotomic Polynomials at x=n, n! and sigma(n)</a>
%F a(n) = 1 + A000203(n)^2.
%F a(n) = 1 + A072861(n). - _Omar E. Pol_, Jun 19 2015
%F a(n) = A002522(A000203(n)). - _Michel Marcus_, Jun 25 2015
%p with(numtheory): A258974:=n->1+sigma(n)^2: seq(A258974(n), n=1..100); # _Wesley Ivan Hurt_, Jul 09 2015
%t Table[1 + DivisorSigma[1, n]^2, {n, 10000}]
%t Table[Cyclotomic[4, DivisorSigma[1, n]], {n, 10000}]
%o (Magma) [(1 + DivisorSigma(1, n)^2): n in [1..50]]; // _Vincenzo Librandi_, Jun 16 2015
%o (PARI) a(n)=sigma(n)^2+1 \\ _Charles R Greathouse IV_, Jun 18 2015
%Y Cf. A000203 (sum of divisors of n).
%Y Cf. A258976 (indices of primes in this sequence), A258977 (corresponding primes).
%K easy,nonn
%O 1,1
%A _Robert Price_, Jun 15 2015
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