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A209914 Number of ways n can be written as a multiple of its reversal A004086(n) +/- a prime p < n. 2
0, 0, 1, 1, 0, 1, 0, 1, 0, 0, 8, 1, 0, 0, 0, 0, 0, 0, 0, 0, 2, 1, 0, 0, 0, 0, 0, 0, 0, 0, 2, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 2, 1, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 0, 1, 0, 0, 0, 0, 2, 3, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,11

COMMENTS

If n is not a multiple of 10, then a(n) < 20. The subsequence { a(10k) }, however, is unbounded. In particular, a(10^k)=2*A006880(k).

LINKS

Table of n, a(n) for n=0..83.

EXAMPLE

a(10)=8 because R(10)=01=1 and 10 = 3*1 + 7 = 5*1 + 5 = 7*1 + 3 = 8*1 + 2 = 12*1 - 2 = 13*1 - 3 = 15*1 - 5 = 17*1 - 7.

PROG

(PARI) a(n)={my(r=A004086(n)); sum(k=1, (2*n-1)\(r+!r), isprime(abs(n-k*r)))}

CROSSREFS

Cf. A209063.

Sequence in context: A180738 A076107 A076952 * A342980 A094922 A230049

Adjacent sequences:  A209911 A209912 A209913 * A209915 A209916 A209917

KEYWORD

nonn,base

AUTHOR

M. F. Hasler, Mar 15 2012

STATUS

approved

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Last modified May 16 17:38 EDT 2022. Contains 353719 sequences. (Running on oeis4.)