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A332217 Numbers k for which the 2-adic valuation of sigma(k) is zero and its 3-adic valuation is 1 (so that sigma(k) is an odd multiple of 3, but not of 9). 3
2, 8, 18, 49, 50, 72, 128, 162, 169, 196, 200, 242, 361, 441, 450, 512, 578, 648, 676, 784, 961, 968, 1058, 1152, 1225, 1250, 1369, 1444, 1458, 1521, 1682, 1764, 1800, 1849, 2178, 2312, 2704, 3136, 3200, 3249, 3362, 3721, 3844, 3969, 4050, 4225, 4232, 4418, 4489, 4608, 4802, 4900, 5000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10000

Index entries for sequences related to sigma(n)

FORMULA

{n: A000035(A000203(n))*A007949(A000203(n))==1}.

MATHEMATICA

Select[Range[5*10^3], IntegerExponent[DivisorSigma[1, #], {2, 3}] === {0, 1} &] (* Michael De Vlieger, Feb 12 2020 *)

PROG

(PARI) isA332217(n) = ((sigma(n)%2)&&(valuation(sigma(n), 3)==1));

CROSSREFS

Subsequence of A067051, which is a subsequence of A028982.

Cf. A332218 (a subsequence).

Cf. A000203, A007949, A332216.

Sequence in context: A246148 A201348 A102713 * A249763 A114723 A267638

Adjacent sequences:  A332214 A332215 A332216 * A332218 A332219 A332220

KEYWORD

nonn

AUTHOR

Antti Karttunen, Feb 11 2020

STATUS

approved

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Last modified September 23 02:41 EDT 2021. Contains 347609 sequences. (Running on oeis4.)