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 A039594 Hexamorphic numbers: k such that the k-th hexagonal number ends with k. 1
 1, 5, 6, 25, 26, 50, 51, 75, 76, 125, 376, 500, 501, 625, 876, 4376, 5000, 5001, 5625, 9376, 40625, 50000, 50001, 59376, 90625, 109376, 390625, 500000, 500001, 609376, 890625, 2109376, 2890625, 5000000, 5000001, 7109376, 7890625, 12890625, 37109376, 50000000, 50000001, 62890625, 87109376 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS k values for the sequence A038494. These are also, whenever m == 6, 14, 30, or 38 (mod 40) the numbers k such that the k-th m-gonal number ends in k. - Robert Dawson, Jul 09 2018 REFERENCES D. Wells, The Penguin Dictionary of Curious and Interesting Numbers, Penguin Book, p. 104. C. A. Pickover, Computers and Imagination, 1991. C. A. Pickover, Hexamorphic numbers, in Hexagonal cats Ch. 63 in Wonders of Numbers: Adventures in Mathematics, Mind, and Meaning, Oxford, England: Oxford University Press, pp. 154, 2001. LINKS EXAMPLE 50 is included because the 50th hexagonal number ends with itself, i.e., 49{50}. MATHEMATICA Select[Range[10^6], Mod[PolygonalNumber[6, #], 10^IntegerLength@ #] == # &] (* Michael De Vlieger, Jul 30 2018 *) PROG (PARI) isok(n) = {my(m = n*(2*n-1)); (m - n) % 10^#Str(n) == 0; } \\ Michel Marcus, Sep 25 2015 CROSSREFS Cf. A038494, A000384. Sequence in context: A160529 A039572 A033042 * A137080 A025622 A116553 Adjacent sequences:  A039591 A039592 A039593 * A039595 A039596 A039597 KEYWORD nonn,base AUTHOR EXTENSIONS More terms from Patrick De Geest, Jun 15 1999 More terms from Michel Marcus, Sep 25 2015 Definition corrected by Altug Alkan, Sep 25 2015 Definition changed by Robert Dawson, Jun 20 2018 Name edited by Michel Marcus, Jul 22 2018 STATUS approved

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Last modified October 15 15:14 EDT 2019. Contains 328030 sequences. (Running on oeis4.)