login
A162948
Numbers with a sum of digits equal to their smallest prime factor.
1
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
1,1
LINKS
FORMULA
{n: A007953(n) = A020639(n)}. - R. J. Mathar, Jul 19 2009
EXAMPLE
133 is in the sequence because 1 + 3 + 3 = 7 and 7 is the smallest prime factor of 133.
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
CROSSREFS
Even terms: A069537.
Sequence in context: A110457 A320584 A209191 * A024768 A024769 A340112
KEYWORD
nonn,base
AUTHOR
Claudio Meller, Jul 18 2009
EXTENSIONS
Single-digit primes added by R. J. Mathar, Jul 19 2009
STATUS
approved