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 A307801 Number of palindromic octagonal numbers with exactly n digits. 2
 3, 0, 0, 1, 0, 0, 0, 0, 4, 0, 0, 2, 3, 1, 0, 1, 0, 0, 1, 0 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Number of terms in A057107 with exactly n digits. LINKS G. J. Simmons, Palindromic powers, J. Rec. Math., 3 (No. 2, 1970), 93-98. [Annotated scanned copy] See page 95. EXAMPLE There is only one 4 digit octagonal number that is palindromic, 8008.  Thus, a(4)=1. MATHEMATICA A057107 = {0, 1, 8, 8008, 120232021, 124060421, 161656161, 185464581, 544721127445, 616947749616, 3333169613333, 3333802083333, 6506939396056, 12212500521221, 5466543663456645, 3310988011108890133, 520752145595541257025, 336753352502205253357633, 5882480463134313640842885, 102573006711888117600375201, 8025741496504444056941475208, 18651903272292929227230915681, 33582545421505050512454528533}; Table[Length[Select[A054910, IntegerLength[#] == n || (n == 1 && # == 0) &]], {n, 20}] (* Robert Price, Apr 29 2019 *) CROSSREFS Cf. A000567, A057107, A057106, A059870, A307790, A307791. Sequence in context: A223074 A192732 A092573 * A186717 A233286 A305802 Adjacent sequences:  A307798 A307799 A307800 * A307802 A307803 A307804 KEYWORD nonn,base,more AUTHOR Robert Price, Apr 29 2019 STATUS approved

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Last modified May 29 09:36 EDT 2020. Contains 334698 sequences. (Running on oeis4.)