A111256 - OEIS

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A111256

a(n) = If Prime[n+2]+Prime[n]+1 is prime then Prime[n+2]+Prime[n]+1 else Prime[n+1]+Prime[n]+1.

6, 11, 17, 19, 29, 31, 41, 43, 53, 67, 73, 79, 89, 97, 107, 113, 127, 129, 139, 151, 157, 163, 181, 191, 199, 205, 211, 217, 223, 241, 259, 271, 277, 289, 307, 309, 321, 337, 347, 353, 361, 373, 389, 391, 409, 411, 439, 451, 461, 463, 473, 491, 499, 509, 521

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OFFSET

1,1

COMMENTS

A switch between two sums of primes when the alternating sum is not prime then a direct sequence prime sum is switched.

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

MATHEMATICA

a=Table[If[PrimeQ[Prime[n + 2] + Prime[n] + 1], Prime[n + 2] + Prime[n] + 1, Prime[n + 1] + Prime[n] + 1], {n, 1, 200}]

If[PrimeQ[#[[3]]+#[[1]]+1], #[[3]]+#[[1]]+1, #[[2]]+#[[1]]+1]&/@Partition[ Prime[ Range[ 100]], 3, 1] (* Harvey P. Dale, Jun 10 2022 *)

CROSSREFS

Sequence in context: A284293 A117800 A118847 * A315506 A315507 A315508

Adjacent sequences: A111253 A111254 A111255 * A111257 A111258 A111259

KEYWORD

nonn

AUTHOR

Roger L. Bagula, Nov 01 2005

STATUS

approved