A320966 Powerful numbers A001694 divisible by a cube > 1.

8, 16, 27, 32, 64, 72, 81, 108, 125, 128, 144, 200, 216, 243, 256, 288, 324, 343, 392, 400, 432, 500, 512, 576, 625, 648, 675, 729, 784, 800, 864, 968, 972, 1000, 1024, 1125, 1152, 1296, 1323, 1331, 1352, 1372, 1568, 1600, 1728, 1800, 1936, 1944, 2000, 2025, 2048, 2187, 2197, 2304, 2312, 2401, 2500

Offset

1,1

Comments

Powerful numbers that are not squares of squarefree numbers. - Amiram Eldar, Jun 25 2022

Links

Hugo Pfoertner, Table of n, a(n) for n = 1..10000

Formula

Sum_{n>=1} 1/a(n) = zeta(2)*zeta(3)/zeta(6) - 15/Pi^2 = 0.4237786821... . - Amiram Eldar, Jun 25 2022

Mathematica

Select[Range[2500], (m = MinMax[FactorInteger[#][[;; , 2]]])[[1]] > 1 && m[[2]] > 2 &] (* Amiram Eldar, Jun 25 2022 *)

Prog

(PARI) isA001694(n)=n=factor(n)[, 2]; for(i=1, #n, if(n[i]==1, return(0))); 1 \\ from Charles R Greathouse IV
isA046099(n)=n=factor(n)[, 2]; for(i=1, #n, if(n[i]>2, return(1))); 0
for (k=1, 2500, if(isA001694(k)&&isA046099(k), print1(k, ", ")))

Crossrefs

Cf. A000578, A320965.

Intersection of A001694 and A046099.

A001694 \ A062503.

Sequence in context: A354561 A349306 A245713 * A036966 A076467 A111231

Adjacent sequences: A320963 A320964 A320965 * A320967 A320968 A320969

Keyword

nonn

Author

Hugo Pfoertner, Oct 25 2018

Status

approved