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A095874 If n = k-th prime power then k else 0. 19
1, 2, 3, 4, 5, 0, 6, 7, 8, 0, 9, 0, 10, 0, 0, 11, 12, 0, 13, 0, 0, 0, 14, 0, 15, 0, 16, 0, 17, 0, 18, 19, 0, 0, 0, 0, 20, 0, 0, 0, 21, 0, 22, 0, 0, 0, 23, 0, 24, 0, 0, 0, 25, 0, 0, 0, 0, 0, 26, 0, 27, 0, 0, 28, 0, 0, 29, 0, 0, 0, 30, 0, 31, 0, 0, 0, 0, 0, 32, 0, 33, 0, 34, 0, 0, 0, 0, 0, 35, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(n) = Sum(A010055(n): 1<=k<=n);

a(n) = A065515(n)*(A065515(n)-A065515(n-1)).

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

MATHEMATICA

Join[{1}, Module[{k=2}, Table[If[PrimePowerQ[n], k; k++, 0], {n, 2, 100}]]] (* Harvey P. Dale, Aug 15 2020 *)

PROG

(Haskell)

a095874 n | y == n    = length xs + 1

          | otherwise = 0

          where (xs, y:ys) = span (< n) a000961_list

-- Reinhard Zumkeller, Feb 16 2012, Jun 26 2011

(PARI) a(n)=if(isprimepower(n), sum(i=1, logint(n, 2), primepi(sqrtnint(n, i)))+1, n==1) \\ Charles R Greathouse IV, Apr 29 2015

CROSSREFS

Cf. A000961, A049084.

Sequence in context: A257846 A203572 A195829 * A279385 A267000 A224892

Adjacent sequences:  A095871 A095872 A095873 * A095875 A095876 A095877

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Jun 10 2004

STATUS

approved

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Last modified April 11 00:03 EDT 2021. Contains 342877 sequences. (Running on oeis4.)