A055019 Numbers n such that A051885(p_n) is prime, where p_n=A000040(n) is the n-th prime.

1, 2, 3, 4, 5, 7, 8, 9, 10, 11, 13, 14, 20, 22, 25, 40, 41, 55, 57, 64, 77, 125, 663, 1053, 1414, 1711, 2822, 2956, 4107, 7463

Offset

1,2

Comments

Numbers n such that A051885(A000040(n)) = A054750(n).

No other terms below 10^4.

Links

Table of n, a(n) for n=1..30.

Example

The 125th prime is 691. The least integer with sum of digits 691 is A051885(691) = 8*10^76-1 which is prime. This is the 22nd prime with this property, so a(22)=125.

Prog

(PARI) for(X=1, 300, a=prime(X)%9; b=prime(X)\9; m=(a+1)*10^b-1; if(isprime(m), print([X, prime(X), m]) ) )

Crossrefs

Cf. A054750, A051885.

Sequence in context: A260402 A368087 A191849 * A261466 A172152 A218444

Adjacent sequences: A055016 A055017 A055018 * A055020 A055021 A055022

Keyword

more,nonn,base

Author

Kok Seng Chua (chuaks(AT)ihpc.nus.edu.sg), May 31 2000

Extensions

More terms from Jason Earls, Jun 22 2001

a(27)-a(30) from Max Alekseyev, Dec 09 2011

Status

approved