A249873 In decimal representation: replace each even positioned digit with the digit sum of its double.

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 30, 31, 32, 33, 34, 35, 36

Offset

0,3

Links

Reinhard Zumkeller, Table of n, a(n) for n = 0..10000

Index entries for sequences related to decimal expansion of n

Prog

(Haskell)
a249873 n = if n == 0 then 0 else 100*a249873 n' + 10*a007953 (2*t) + d
            where (n', td) = divMod n 100; (t, d) = divMod td 10
(PARI) a(n) = my(d=Vecrev(digits(n))); forstep (i=2, #d, 2, d[i] = sumdigits(2*d[i])); fromdigits(Vecrev(d)); \\ Michel Marcus, Jan 23 2022

Crossrefs

Cf. A007953, A093017, A028897.

Sequence in context: A275775 A358129 A217556 * A102491 A111706 A118761

Adjacent sequences: A249870 A249871 A249872 * A249874 A249875 A249876

Keyword

nonn,base

Author

Reinhard Zumkeller, Nov 08 2014

Status

approved