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A298972 Number of positive integers k < n such that n occurs in the Reverse-and-Add trajectory of k. 0
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified January 19 18:20 EST 2019. Contains 319309 sequences. (Running on oeis4.)