A047903 a(1) = 13; for n > 0, a(n+1) = a(n) * sum of digits of a(n).

13, 52, 364, 4732, 75712, 1665664, 56632576, 2265303040, 56632576000, 2265303040000, 56632576000000, 2265303040000000, 56632576000000000, 2265303040000000000, 56632576000000000000, 2265303040000000000000

Offset: 1

Author

Miklos SZABO (mike(AT)ludens.elte.hu)

Keywords

• easy
• nonn
• base

Comments

After the 7th element, every second element has the same beginning. a(9+2k) = 40 * a(8+2k) = 40 * 25 * a(7+2k).

Crossrefs

Cf. A047892.

Programs

Mathematica

NestList[# Total[IntegerDigits[#]]&,13,20] (* Harvey P. Dale, Jan 08 2019 *)