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, 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

Offset: 1

Author

Eric M. Schmidt, Dec 16 2017

Keywords

• nonn

Comments

First disagreement with A062383(n-1) 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.

Crossrefs

Cf. A033846.

Programs

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