A298972 Number of positive integers k < n such that n occurs in the Reverse-and-Add trajectory of k.

0, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 2, 2, 0, 1, 0, 4, 0, 1, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 11, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 11, 0, 0, 0, 0, 0, 0, 0, 0

Offset

0,5

Comments

Number of integers k < n such that n occurs in row k of A243238.

For n > 0, a(n) = 0 iff n is a term of A067031.

For n > 0, a(n) > 0 iff n is a term of A067030.

Links

Table of n, a(n) for n=0..85.

Index entries for sequences related to Reverse and Add!

Example

For n = 22: There exist 4 positive integers k < 22 such that 22 occurs in the Reverse-and-Add trajectory of k, namely 5, 10, 11 and 20, so a(22) = 4.

Mathematica

Block[{nn = 85, s}, s = Array[Union@ NestWhileList[# + IntegerReverse@ # &, #, # < nn &, 1, nn] &, nn]; Array[Count[Take[s, # - 1], #, 2] &, nn + 1, 0]] (* Michael De Vlieger, Feb 01 2018 *)

Prog

(PARI) a(n) = my(i=0); for(k=1, n-1, my(x=k); while(x < n, x=x+eval(concat(Vecrev(Str(x))))); if(x==n, i++)); i

Crossrefs

Cf. A056964, A067030, A067031, A243238.

Sequence in context: A162515 A175267 A108045 * A143728 A127368 A112552

Adjacent sequences: A298969 A298970 A298971 * A298973 A298974 A298975

Keyword

nonn,base

Author

Felix Fröhlich, Jan 30 2018

Status

approved