A162948 Numbers with a sum of digits equal to their smallest prime factor.

2, 3, 5, 7, 20, 21, 110, 111, 133, 200, 201, 209, 247, 407, 481, 511, 629, 803, 1010, 1011, 1100, 1101, 1141, 1387, 1417, 1651, 1679, 1853, 2000, 2001, 2023, 2119, 2159, 2353, 2401, 2771, 3031, 3077, 3097, 3383, 3439, 3523, 3749, 3781, 4577, 4607, 4913, 5149, 5161

Offset: 1

Author

Claudio Meller, Jul 18 2009

Keywords

• nonn
• base

Examples

			133 is in the sequence because 1 + 3 + 3 = 7 and 7 is the smallest prime factor of 133.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf: A007953, A020639.

Even terms: A069537.

Programs

Maple

A007953 := proc(n) local d; add(d,d=convert(n,base,10)) ; end:
A020639 := proc(n) min(op(numtheory[factorset](n) )) ; end:
isA162948 := proc(n) RETURN( A007953(n) = A020639(n)) ; end:
for n from 1 to 6000 do if isA162948(n) then printf("%d,",n) ; fi; od: # R. J. Mathar, Jul 19 2009

Formula

{n: A007953(n) = A020639(n)}. - R. J. Mathar, Jul 19 2009

Extensions

Single-digit primes added by R. J. Mathar, Jul 19 2009