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A258974 a(n) = 1 + sigma(n)^2. 3
2, 10, 17, 50, 37, 145, 65, 226, 170, 325, 145, 785, 197, 577, 577, 962, 325, 1522, 401, 1765, 1025, 1297, 577, 3601, 962, 1765, 1601, 3137, 901, 5185, 1025, 3970, 2305, 2917, 2305, 8282, 1445, 3601, 3137, 8101, 1765, 9217, 1937, 7057, 6085, 5185, 2305 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Robert Price, Table of n, a(n) for n = 1..10000

OEIS Wiki, Cyclotomic Polynomials at x=n, n! and sigma(n)

FORMULA

a(n) = 1 + A000203(n)^2.

a(n) = 1 + A072861(n). - Omar E. Pol, Jun 19 2015

a(n) = A002522(A000203(n)). - Michel Marcus, Jun 25 2015

MAPLE

with(numtheory): A258974:=n->1+sigma(n)^2: seq(A258974(n), n=1..100); # Wesley Ivan Hurt, Jul 09 2015

MATHEMATICA

Table[1 + DivisorSigma[1, n]^2, {n, 10000}]

Table[Cyclotomic[4, DivisorSigma[1, n]], {n, 10000}]

PROG

(MAGMA) [(1 + DivisorSigma(1, n)^2): n in [1..50]]; // Vincenzo Librandi, Jun 16 2015

(PARI) a(n)=sigma(n)^2+1 \\ Charles R Greathouse IV, Jun 18 2015

CROSSREFS

Cf. A000203 (sum of divisors of n).

Cf. A258976 (indices of primes in this sequence), A258977 (corresponding primes).

Sequence in context: A304805 A214086 A127492 * A077247 A082939 A074069

Adjacent sequences:  A258971 A258972 A258973 * A258975 A258976 A258977

KEYWORD

easy,nonn

AUTHOR

Robert Price, Jun 15 2015

STATUS

approved

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Last modified April 19 11:18 EDT 2019. Contains 322264 sequences. (Running on oeis4.)