A154539 Primes p such that (smallest digit of p) + (number of occurrences of smallest digit of p) is prime.

2, 11, 13, 17, 19, 23, 29, 31, 41, 47, 61, 67, 71, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 311, 313, 317, 331, 337, 353, 373, 383, 419, 421, 431, 433

Offset

1,1

Links

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

Example

2 is the smallest digit of 2, and it appears once; 2 and 2+1 are prime, so a(1) = 2.
1 is the smallest digit of 11 and it appears twice; 11 and 1+2 are prime, so a(2) = 11.
1 is the smallest digit of 13 and it appears once; 13 and 1+1 are prime, so a(3) = 13.

Maple

frequdig := proc(n, dig) local f, d ; f := 0 ; for d in convert(n, base, 10) do if d = dig then f :=f+1; end if; end do; f ; end proc:
A054054 := proc(n) min(op(convert(n, base, 10)) ) ; end proc:
for n from 1 to 500 do p := ithprime(n) ; sdg := A054054(p) ; a := sdg +frequdig(p, sdg) ; if isprime(a) then printf("%d, ", p ) ; end if; end do: # R. J. Mathar, May 05 2010

Mathematica

psdQ[n_]:=Module[{m=Min[IntegerDigits[n]]}, PrimeQ[m+DigitCount[n, 10, m]]]; Select[Prime[Range[100]], psdQ] (* Harvey P. Dale, Nov 26 2019 *)

Crossrefs

Sequence in context: A116437 A048867 A113626 * A137238 A048521 A172071

Adjacent sequences: A154536 A154537 A154538 * A154540 A154541 A154542

Keyword

nonn,base,less

Author

Juri-Stepan Gerasimov, Jan 11 2009

Extensions

Entries checked by R. J. Mathar, May 05 2010

Status

approved