

A071218


Numbers k such that the largest prime factor of the sum of the two consecutive primes prime(k) + prime(k+1) is at most k.


1



2, 3, 4, 5, 6, 7, 8, 10, 13, 14, 15, 16, 17, 18, 20, 21, 22, 25, 26, 27, 28, 30, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 52, 53, 55, 56, 57, 59, 60, 61, 62, 64, 65, 66, 68, 69, 70, 72, 73, 74, 78, 79, 80, 81, 82, 83, 85, 88, 89, 90, 91, 92, 94
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OFFSET

1,1


LINKS

Table of n, a(n) for n=1..71.


FORMULA

If A071216(k) <= k, then k is in this sequence.


EXAMPLE

k=25: prime(25) + prime(26) = 97 + 101 = 198 = 2*3*3*11 and 11 < 25, so 25 is in this sequence;


MATHEMATICA

Select[Range[94], FactorInteger[Prime[#] + Prime[# + 1]][[1, 1]] <= # &] (* Giovanni Resta, Jul 13 2018 *)


PROG

(PARI) isok(n) = vecmax(factor(prime(n)+prime(n+1))[, 1]) <= n; \\ Michel Marcus, Jul 09 2018


CROSSREFS

Cf. A006530, A001043, A071216, A071217, A071219.
Sequence in context: A263363 A061920 A062010 * A215775 A236310 A005709
Adjacent sequences: A071215 A071216 A071217 * A071219 A071220 A071221


KEYWORD

nonn


AUTHOR

Labos Elemer, May 17 2002


EXTENSIONS

Edited by Jon E. Schoenfield, Jul 08 2018


STATUS

approved



