A171603 - OEIS

A171603

Lesser of two consecutive primes such that half-sums are product of two distinct primes.

5, 13, 19, 23, 31, 37, 67, 83, 89, 109, 127, 131, 199, 211, 251, 271, 307, 331, 379, 383, 389, 443, 449, 467, 487, 499, 509, 563, 661, 683, 719, 769, 797, 877, 929, 937, 971, 997, 1009, 1123, 1163, 1201, 1223, 1231, 1237, 1283, 1291, 1297, 1307, 1459, 1511

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..51.

EXAMPLE

(5+7)/2=6->2*3, (13+17)/2=15->3*5,..

MATHEMATICA

f[n_]:=Last/@FactorInteger[n]=={1, 1}; lst={}; Do[p=Prime[n]; q=Prime[n+1]; s=(p+q)/2; If[f[s], AppendTo[lst, p]], {n, 6!}]; lst

CROSSREFS

Cf. A171602

Sequence in context: A209663 A156111 A162174 * A118915 A084442 A023270

Adjacent sequences: A171600 A171601 A171602 * A171604 A171605 A171606

KEYWORD

nonn

AUTHOR

Vladimir Joseph Stephan Orlovsky, Dec 12 2009

STATUS

approved

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