A256577 Sum_{k>=0} (d_k)^(k+1)*10^k, where Sum_{k>=0} (d_k)*10^k is the decimal expansion of n.

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 250, 251, 252, 253, 254, 255, 256, 257, 258, 259, 360, 361, 362, 363, 364, 365, 366, 367, 368, 369, 490

Offset

0,3

Comments

a(n) = n when 0 <= n < 20 or 10^i <= n < 10^i + 20 for some i>1.

a(n) = n if and only if every digit of n (in base 10), except possibly the ones digit, is 0 or 1. Otherwise, n < a(n). - Danny Rorabaugh, Apr 02 2015

Links

Michael De Vlieger, Table of n, a(n) for n = 0..10000

Example

a(19) = 1^2 * 10^1 + 9^1 * 10^0 = 19.
a(20) = 2^2 * 10^1 + 0^1 * 10^0 = 40.
a(40) = 4^2 * 10^1 + 0^1 * 10^0 = 160.
a(199) = 1^3 * 10^2 + 9^2 * 10^1 + 9^1 * 10^0 = 100 + 810 + 9 = 919.

Mathematica

Array[Total@ MapIndexed[#1^(#2)*10^(#2 - 1) & @@ {#1, First[#2]} &, Reverse@ IntegerDigits[#]] &, 71, 0] (* Michael De Vlieger, Nov 16 2022 *)

Prog

(PARI) vector(80, n, d = digits(n); sum(k=1, #d, d[k]^(#d-k+1)*10^(#d-k))) \\ Michel Marcus, Apr 09 2015

Crossrefs

Cf. A066566 (first 39 terms identical).

Cf. A255073 (primes that remain prime, no carry).

Sequence in context: A250243 A341936 A066566 * A067080 A008554 A055644

Adjacent sequences: A256574 A256575 A256576 * A256578 A256579 A256580

Keyword

base,nonn,easy

Author

Michael De Vlieger, Apr 02 2015

Extensions

Name and comments corrected by Paul Tek, Apr 11 2015

Status

approved