A157678 Numbers k such that k + floor(average of digits of k) is prime.

1, 12, 16, 27, 30, 34, 38, 41, 56, 63, 67, 70, 74, 89, 92, 96, 101, 102, 105, 107, 112, 125, 128, 130, 136, 146, 147, 154, 161, 164, 168, 175, 186, 188, 190, 193, 208, 210, 219, 226, 229, 231, 236, 237, 247, 254, 258, 265, 273, 276, 278, 280, 290, 305, 308, 309

Offset

1,2

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Example

n = 89 -> 89 + floor((8+9)/2) = 89 + 8 = 97 (prime).
n = 190 -> 190 + floor((1+9+0)/3) = 190 + 3 = 193 (prime).

Maple

a := proc (n) local nn: nn := convert(n, base, 10): if isprime(n+floor(add(nn[j], j = 1 .. nops(nn))/nops(nn))) = true then n else end if end proc: seq(a(n), n = 1 .. 350); # Emeric Deutsch, Mar 07 2009

Prog

(PARI) is(n)=isprime(sumdigits(n)\#digits(n)+n) \\ Charles R Greathouse IV, Dec 27 2013

Crossrefs

Cf. A172367.

Sequence in context: A077617 A182074 A192609 * A334560 A357631 A109240

Adjacent sequences: A157675 A157676 A157677 * A157679 A157680 A157681

Keyword

nonn,base

Author

Kyle D. Balliet, Mar 04 2009

Extensions

Corrected and extended by Emeric Deutsch, Mar 07 2009

Status

approved