A270311 Indices of primes ending with the same decimal digit as the previous or next prime.

34, 35, 42, 43, 53, 54, 61, 62, 68, 69, 80, 81, 82, 83, 101, 102, 106, 107, 115, 116, 125, 126, 127, 128, 138, 139, 141, 142, 145, 146, 154, 155, 157, 158, 172, 173, 175, 176, 177, 178, 191, 192, 193, 194, 204, 205, 222, 223, 233, 234, 258, 259, 260, 266, 267, 269, 270, 279, 280, 289, 290, 306, 307

Offset: 1

Author

Francois Alcover, Mar 15 2016

Keywords

• nonn
• base

Links

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

Crossrefs

Cf. A270310.

Programs

Mathematica

Select[Range@ 307, Function[k, Or[k == Mod[NextPrime@ Prime@ #, 10], k == Mod[NextPrime[Prime@ #, -1], 10]]]@ Mod[Prime@ #, 10] &] (* Michael De Vlieger, Mar 15 2016 *)
PrimePi/@Select[Partition[Prime[Range[350]],3,1],Mod[#[[2]],10]==Mod[#[[1]],10]||Mod[#[[2]],10]==Mod[#[[3]],10]&][[;;,2]] (* Harvey P. Dale, Mar 07 2024 *)

Extensions

More terms from Michael De Vlieger, Mar 15 2016