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 A000015 Smallest prime power >= n. 10
 1, 2, 3, 4, 5, 7, 7, 8, 9, 11, 11, 13, 13, 16, 16, 16, 17, 19, 19, 23, 23, 23, 23, 25, 25, 27, 27, 29, 29, 31, 31, 32, 37, 37, 37, 37, 37, 41, 41, 41, 41, 43, 43, 47, 47, 47, 47, 49, 49, 53, 53, 53, 53, 59, 59, 59, 59, 59, 59, 61, 61, 64, 64, 64, 67, 67, 67, 71, 71, 71, 71, 73 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS David W. Wilson, Table of n, a(n) for n = 1..10000 Eric Weisstein's World of Mathematics, Prime Power FORMULA a(A110654(n+1)) = A188666(n). - Reinhard Zumkeller, Apr 25 2011, corrected by M. F. Hasler, Jul 25 2015 a(n) = A188666(2n-1). - M. F. Hasler, Jul 25 2015 MAPLE N:= 1000: # to get all terms <= N Primes:= select(isprime, {\$1..N}): PPs:= {1} union Primes: for k from 1 to ilog2(N) do PPs:= PPs union map(`^`, select(`<=`, Primes, floor(N^(1/k))), k) od: PPs:= sort(convert(PPs, list)): 1, seq(PPs[i]\$(PPs[i]-PPs[i-1]), i=2..nops(PPs)); # Robert Israel, Jul 23 2015 MATHEMATICA Insert[Table[m:=n; While[Not[Length[FactorInteger[m]]==1], m++ ]; m, {n, 2, 100}], 1, 1] (* Stefan Steinerberger, Apr 17 2006 *) a[n_] := NestWhile[# + 1 &, n, Not@*PrimePowerQ]; (* Matthew House, Jul 14 2015, v6.0+ *) a[ n_] := If[ n < 2, Boole[n == 1], Module[{m = n}, While[ ! PrimePowerQ[ m], m++]; m]]; (* Michael Somos, Mar 06 2018 *) a[ n_] := If[ n < 1, 0, Module[{m = n}, While[ Length[ FactorInteger @ m ] != 1, m++]; m]]; (* Michael Somos, Mar 06 2018 *) PROG (PARI) {a(n) = if( n<1, 0, while(matsize(factor(n))[1]>1, n++); n)}; /* Michael Somos, Jul 16 2002 */ (PARI) a(n)=if(n>1, while(!isprimepower(n), n++)); n \\ Charles R Greathouse IV, Feb 01 2013 (Sage) [next_prime_power(n) for n in range(72)] # Zerinvary Lajos, Jun 13 2009 (Haskell) a000015 n = a000015_list !! (n-1) a000015_list = 1 : concat (zipWith(\pp qq -> replicate (fromInteger (pp - qq)) pp) (tail a000961_list) a000961_list) -- Reinhard Zumkeller, Nov 17 2011, Apr 25 2011 CROSSREFS Cf. A000961, A031218. Sequence in context: A343271 A363897 A114707 * A306369 A291784 A291934 Adjacent sequences: A000012 A000013 A000014 * A000016 A000017 A000018 KEYWORD nonn,easy AUTHOR N. J. A. Sloane EXTENSIONS More terms from Michael Somos, Jul 16 2002 STATUS approved

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Last modified September 22 08:09 EDT 2023. Contains 365519 sequences. (Running on oeis4.)