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A030690 Smallest nontrivial extension of n-th square which is a cube. 4
125, 4096, 9261, 166375, 250047, 3652264, 4913, 64000, 8120601, 1000, 12167, 1442897, 16974593, 19683, 225866529, 25672375, 28934443, 3241792, 3616805375, 40001688, 4410944, 4843965888, 529475129, 5764224257 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Chai Wah Wu, Table of n, a(n) for n = 1..10000

PROG

(Python)

from gmpy2 import iroot

def A030690(n):

    d, nd = 10, 10*n**2

    while True:

        x = (iroot(nd-1, 3)[0]+1)**3

        if x < nd+d:

            return int(x)

        d *= 10

        nd *= 10 # Chai Wah Wu, May 24 2016

CROSSREFS

Cf. A030691.

Sequence in context: A265470 A017331 A264139 * A017451 A241034 A265931

Adjacent sequences:  A030687 A030688 A030689 * A030691 A030692 A030693

KEYWORD

nonn,base

AUTHOR

Patrick De Geest

STATUS

approved

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Last modified June 25 06:06 EDT 2016. Contains 274195 sequences.