A066776 Numbers n such that A043347(n) is a prime.

1, 2, 3, 4, 69, 113

Offset: 1

Author

Joseph L. Pe, Jan 14 2002

Keywords

• base
• hard
• nonn

Comments

A043347(170) already has over a thousand digits.

Programs

Mathematica

a[n_] := (k = Prime[ Floor[n^(3/2)]] + 6; l = Sum[ Prime[i], {i, 1, n - 1} ]; b = ""; Do[ b = StringJoin[b, ToString[ Prime[i]]], {i, 1, k} ]; Return[ ToExpression[ StringTake[ StringDrop[b, l], Prime[n]]]]); Do[ If[ PrimeQ[ a[n]], Print[n]], {n, 1, 180} ]