A051955 - OEIS

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A051955

a(n) = smallest palindrome > a(n-1) such that a(1)*a(2)*...*a(n) + 1 and a(1)*a(2)*...*a(n) - 1 are primes.

4, 363, 434, 484, 494, 636, 4004, 46864, 47474, 135531, 695596, 1793971, 1826281, 1933391, 4700074, 4785874, 4806084, 6462646, 6574756, 9558559, 15399351, 46288264, 53500535, 57499475, 150787051, 185808581, 197636791, 226686622

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

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..28.

MATHEMATICA

a[1] = 4; a[n_] := a[n] = For[k = a[n-1]+1, True, k++, id = IntegerDigits[k]; If[id == Reverse[id], p = Product[a[j], {j, 1, n - 1}]*k + 1; If[PrimeQ[p] && PrimeQ[p-2], Return[k]]]]; Table[Print["a(", n, ") = ", a[n]]; a[n], {n, 1, 28}] (* Jean-François Alcover, Jul 30 2017 *)

CROSSREFS

Cf. A051896, A051954.

Subsequence of A002113.

Sequence in context: A203034 A215827 A366469 * A177114 A109760 A051181

Adjacent sequences: A051952 A051953 A051954 * A051956 A051957 A051958

KEYWORD

nice,nonn,base

AUTHOR

Felice Russo, Dec 21 1999

EXTENSIONS

a(12)-a(28) from Donovan Johnson, Feb 17 2010

STATUS

approved