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A227279 Squares of odd primes and twice squares of odd primes. 0
9, 18, 25, 49, 50, 98, 121, 169, 242, 289, 338, 361, 529, 578, 722, 841, 961, 1058, 1369, 1681, 1682, 1849, 1922, 2209, 2738, 2809, 3362, 3481, 3698, 3721, 4418, 4489, 5041, 5329, 5618, 6241, 6889, 6926, 7442, 7921, 8978, 9409, 10082, 10201, 10609, 10658, 11449, 11881, 12482, 12769, 13778 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Essentially, the union of A001248 and A143928.

sigma(a(n)) = (a(n) + sqrt(a(n)) + 1) * (omega(a(n))^2 - omega(a(n)) + 1). omega(a(n)) = 2 - (a(n) mod 2). Omega(a(n)) = 3 - (a(n) mod 2). mu(a(n)) = 0. rad(a(n)) = sqrt( a(n)*omega(a(n)) ).

LINKS

Table of n, a(n) for n=1..51.

EXAMPLE

49 is in the sequence since 49 = 7^2 (the square of an odd prime). 18 is in the sequence since 18 = 2*3^2 (twice the square of an odd prime).

MATHEMATICA

max = 13778; Union[Prime[Range[2, PrimePi[Sqrt[max]]]]^2, 2Prime[Range[2, PrimePi[Sqrt[max/2]]]]^2] (* Alonso del Arte, Jul 04 2013 *)

CROSSREFS

Cf. A028982, A001248, A143928.

Sequence in context: A072502 A195268 A328252 * A102042 A121282 A205716

Adjacent sequences:  A227276 A227277 A227278 * A227280 A227281 A227282

KEYWORD

nonn,easy

AUTHOR

Wesley Ivan Hurt, Jul 04 2013

STATUS

approved

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Last modified November 18 07:22 EST 2019. Contains 329252 sequences. (Running on oeis4.)