A342979 a(1) = 2. For n > 1, a(n) is the smallest prime p > a(n-1) such that a(n-1) + p is a 4-almost prime (A014613).

2, 79, 131, 163, 167, 173, 191, 199, 263, 269, 277, 281, 283, 337, 349, 359, 367, 373, 397, 401, 419, 431, 439, 491, 521, 541, 557, 593, 599, 607, 613, 617, 619, 659, 677, 733, 751, 757, 761, 811, 857, 877, 907, 911, 919, 1009, 1021, 1039, 1051, 1097, 1129, 1163, 1181, 1237, 1279

Offset

1,1

Comments

Minimal difference 2 occurs at positions 12, 32, 86, 118, 155, 242, 345, 427, 430, 517, .... E.g., 2 = 283 - 281 = 619 - 617 = 2083 - 2081.

Links

Table of n, a(n) for n=1..55.

Example

2 + 79 = 81 = A014613(8), 79 + 131 = 210 = A014613(27).

Mathematica

s = {2}; p = 2; Do[q = NextPrime[p]; While[4 != PrimeOmega[p + q], q = NextPrime[q]]; AppendTo[s, p = q], {55}]; s

Crossrefs

Cf. A000040, A014613.

Sequence in context: A231240 A197101 A245674 * A166052 A045484 A113152

Adjacent sequences: A342976 A342977 A342978 * A342980 A342981 A342982

Keyword

nonn

Author

Zak Seidov, Apr 02 2021

Status

approved