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A177215 Numbers k that are the products of two distinct primes such that 2*k-1, 4*k-3, 8*k-7, 16*k-15, 32*k-31 and 64*k-63 are also products of two distinct primes. 6
694, 3403, 4714, 5062, 5353, 7495, 11293, 12139, 13798, 14191, 19735, 21439, 22585, 24277, 25009, 25399, 26734, 26899, 31261, 32959, 35299, 36199, 44869, 48949, 49471, 50797, 58003, 60181, 62521, 70759, 72397, 73909, 75631, 79021, 83086 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..35.

EXAMPLE

694 is a term because 694 = 2*347, 2*694 - 1 = 1387 = 19*73, 4*694 - 1 = 2773 = 47*59, 8*694 - 1 = 5545 = 5*1109, 16*694 - 1 = 11089 = 13*853, 32*694 - 1 = 22177 = 67*331, and 64*694 - 1 = 44353 = 17*3609.

MATHEMATICA

f[n_]:=Last/@FactorInteger[n]=={1, 1}; lst={}; Do[If[f[n]&&f[2*n-1]&&f[4*n-3]&&f[8*n-7]&&f[16*n-15]&&f[32*n-31]&&f[64*n-63], AppendTo[lst, n]], {n, 0, 9!}]; lst

CROSSREFS

Cf. A006881, A177210, A177211, A177212, A177213, A177214.

Sequence in context: A049356 A020385 A004242 * A185861 A115493 A214165

Adjacent sequences:  A177212 A177213 A177214 * A177216 A177217 A177218

KEYWORD

nonn

AUTHOR

Vladimir Joseph Stephan Orlovsky, May 04 2010

STATUS

approved

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Last modified October 19 22:05 EDT 2021. Contains 348095 sequences. (Running on oeis4.)