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 A354981 a(n) = 1 if n = 2 * p^k, with p an odd prime and k >= 1, otherwise 0. 1
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 OFFSET 1 LINKS Antti Karttunen, Table of n, a(n) for n = 1..100000 Index entries for characteristic functions FORMULA a(n) = [n == 2 (mod 4)] * A069513(n/2), where [ ] is the Iverson bracket. For n > 4, a(n) = A211487(n) - A174275(n). MATHEMATICA a[n_] := If[IntegerExponent[n, 2] == 1 && PrimePowerQ[n/2], 1, 0]; Array[a, 100] ( * Amiram Eldar, Jun 15 2022 *) Module[{nn=150, c}, c=Union[Flatten[Table[2 p^k, {p, Prime[Range[2, 35]]}, {k, 5}]]]; Table[If[ MemberQ[ c, k], 1, 0], {k, nn}]] (* Harvey P. Dale, Sep 18 2023 *) PROG (PARI) A354981(n) = (2==(n%4) && isprimepower(n/2)); CROSSREFS Characteristic function of A278568 \ {2}. Cf. A069513, A174275, A211487, A354108. Sequence in context: A361463 A104853 A358775 * A231600 A347579 A280710 Adjacent sequences: A354978 A354979 A354980 * A354982 A354983 A354984 KEYWORD nonn AUTHOR Antti Karttunen, Jun 15 2022 STATUS approved

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Last modified September 8 22:12 EDT 2024. Contains 375759 sequences. (Running on oeis4.)