A171607 Expressible as A*B^A in a nontrivial way.

8, 18, 24, 32, 50, 64, 72, 81, 98, 128, 160, 162, 192, 200, 242, 288, 324, 338, 375, 384, 392, 450, 512, 578, 648, 722, 800, 882, 896, 968, 1024, 1029, 1058, 1152, 1215, 1250, 1352, 1458, 1536, 1568, 1682, 1800, 1922, 2048, 2178, 2187, 2312, 2450, 2500, 2592

Offset

1,1

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

R. Munafo, Generalized Cullen and Woodall Numbers

Formula

a(n) = 2n^2 - O(n^(5/3)). - Charles R Greathouse IV, Feb 19 2017

Example

8=2*2^2. 24=3*2^3. 375=3*5^3.

Prog

(PARI) is(n)=if(n<8, return(0)); for(a=2, logint(n\2, 2), if(n%a==0 && ispower(n/a, a), return(1))); 0 \\ Charles R Greathouse IV, Feb 19 2017
(PARI) list(lim)=my(v=List()); if(lim<8, return([])); for(a=2, logint(lim\2, 2), for(b=2, sqrtnint(lim\a, a), listput(v, a*b^a))); Set(v) \\ Charles R Greathouse IV, Feb 19 2017

Crossrefs

Cf. A171606. Union of the "KN^K" sequences A001105, A117642, A141046, ... or of the "NK^N" sequences A036289, A036290, A018215, A036291, ... but omitting the trivial initial terms.

Sequence in context: A051810 A034055 A043101 * A039278 A045043 A043881

Adjacent sequences: A171604 A171605 A171606 * A171608 A171609 A171610

Keyword

nonn

Author

Robert Munafo, Dec 12 2009

Status

approved