A210734 -id:A210734 - cp's OEIS frontend

A286661 Primes of form A038396(n) - 1 or A038396(n) + 1.

3, 41, 43, 641, 643, 8641, 108643, 18161412108641, 525048464442403836343230282624222018161412108643, 646260585654525048464442403836343230282624222018161412108641

Offset: 1

XU Pingya, May 12 2017

a(11) = A038396(42) + 1 = 84...43, a(12) = A038396(54) + 1 = 108...43;
a(13) = A038396(185) + 1 = 370...43, a(14) = A038396(199) - 1 = 398...41;
a(15) = A038396(224) + 1 = 448...43, a(16) = A038396(248) - 1 = 496...41;
a(17) = A038396(346) - 1 = 692...41, a(18) = A038396(947) - 1 = 1894...41.
a(19) (if it exists) will be more than  A038396(3000).
a(2) and a(3) are a pair of twin primes, a(4) and a(5) also.

Eric Weisstein's World of Mathematics, Consecutive Number Sequences

Cf. A038396, A019520, A210734.

Select[#, PrimeQ] &@ Flatten@ Table[{# - 1, # + 1} &@ FromDigits@ Flatten@ Reverse@ Take[#, n], {n, Length@ #}] &@ Array[IntegerDigits[2 #] &, 40] (* Michael De Vlieger, May 14 2017 *)

A387245 Numbers k such that (the concatenation of the first k positive even numbers) + 1 is prime.

Original entry on oeis.org

1, 5, 9, 24, 1400, 8915

Offset: 1

Shyam Sunder Gupta, Aug 24 2025

a(6) = 8915 corresponds to a 39024-digit probable prime. a(7) > 15000.

The corresponding primes are a subsequence of A210734. - Michael S. Branicky, Aug 24 2025

			5 is a term since 246810 + 1 = 246811 is prime.

Cf. A019520, A069048, A210734.

{k | A019520(k) + 1 is prime}. - Michael S. Branicky, Aug 24 2025

cp's OEIS Frontend

A286661 Primes of form A038396(n) - 1 or A038396(n) + 1.

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