A038494 - OEIS

A038494

Images of hexamorphic numbers: suppose k-th hexagonal number H(k) (A000384) ends in k; sequence gives positive values of H(k).

1, 45, 66, 1225, 1326, 4950, 5151, 11175, 11476, 31125, 282376, 499500, 501501, 780625, 1533876, 38294376, 49995000, 50015001, 63275625, 175809376, 3300740625, 4999950000, 5000150001, 7050959376, 16425690625, 23926109376

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

REFERENCES

D. Wells, The Penguin Dictionary of Curious and Interesting Numbers, Penguin Book, p. 104.

C. 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

Table of n, a(n) for n=1..26.

EXAMPLE

45 is included because it is the 5th hexagonal number and it ends in 5.

MATHEMATICA

Select[Array[{PolygonalNumber[6, #], #} &, 10^6], FromDigits[Take[IntegerDigits[#], -IntegerLength@ #2]] == #2 & @@ # &][[All, 1]] (* Michael De Vlieger, Jun 30 2018 *)

PROG

(PARI) lista(nn) = {for (n=1, nn, m = n*(2*n-1); if ((m - n) % 10^#Str(n) == 0, print1(m, ", ")); ); } \\ Michel Marcus, Sep 25 2015

CROSSREFS

Cf. A039594, A000384.

Sequence in context: A046426 A056776 A172466 * A026043 A372291 A330850

Adjacent sequences: A038491 A038492 A038493 * A038495 A038496 A038497

KEYWORD

nonn,base

AUTHOR

Felice Russo

EXTENSIONS

More terms from Patrick De Geest, Jun 15 1999

Name corrected by Robert Dawson, Jun 20 2018

STATUS

approved