

A296613


Smallest k such that either k >= n and k is a power of 2, or k >= 5n/3 and the prime divisors of k are precisely 2 and 5.


1



1, 2, 4, 4, 8, 8, 8, 8, 16, 16, 16, 16, 16, 16, 16, 16, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 128, 128
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OFFSET

1,2


COMMENTS

First disagreement with A062383(n1) is at n = 129.
For n > 2, a(n) is not squarefree.  Iain Fox, Dec 17 2017


LINKS

Eric M. Schmidt, Table of n, a(n) for n = 1..10000
Bernadette Faye, Florian Luca, Pieter Moree, On the discriminator of Lucas sequences, arXiv:1708.03563 [math.NT], 2017, Theorem 1.


PROG

(PARI) a(n) = for(k=n, +oo, if(k == 2^valuation(k, 2)  (k >= 5*n/3 && factor(k)[, 1] == [2, 5]~), return(k))) \\ Iain Fox, Dec 17 2017


CROSSREFS

Cf. A033846.
Sequence in context: A265544 A290221 A098820 * A062383 A034583 A076347
Adjacent sequences: A296610 A296611 A296612 * A296614 A296615 A296616


KEYWORD

nonn


AUTHOR

Eric M. Schmidt, Dec 16 2017


STATUS

approved



