A103125 4-Smith numbers.

2401, 5010, 7000, 10005, 10311, 10410, 10411, 11060, 11102, 11203, 12103, 13002, 13021, 13101, 14001, 14101, 14210, 20022, 20121, 20203, 20401, 21103, 21112, 21120, 21201, 22040, 22101, 22201, 23030, 30003, 30031, 30320, 31002, 31101

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..600 from Harvey P. Dale)

Shyam Sunder Gupta, Smith Numbers.

Wayne L. McDaniel, The Existence of infinitely Many k-Smith numbers, Fibonacci Quarterly, Vol. 25, No. 1 (1987), pp. 76-80.

Example

2401 is a 4-Smith number because the sum of the digits of its prime factors, i.e., Sp(2401) = Sp(7*7*7*7) = 7 + 7 + 7 + 7 = 28, which is equal to 4 times the digit sum of 2401, i.e., 4*S(2401) = 4*(2 + 4 + 0 + 1) = 28.

Mathematica

sn4Q[n_]:=Module[{a=Total[Flatten[IntegerDigits/@(Table[First[#], {Last[ #]}]&/@FactorInteger[n])]], b=4Total[IntegerDigits[n]]}, a==b] (* Harvey P. Dale, Oct 03 2011 *)

Crossrefs

Cf. A006753.

Sequence in context: A186488 A186487 A043396 * A074384 A016924 A016984

Adjacent sequences: A103122 A103123 A103124 * A103126 A103127 A103128

Keyword

base,nonn

Author

Shyam Sunder Gupta, Mar 16 2005

Status

approved