

A094534


Centered hexamorphic numbers: the kth centered hexagonal number, 3k(k1)+1, ends in k.


1



1, 7, 17, 51, 67, 167, 251, 417, 501, 667, 751, 917, 1251, 1667, 5001, 5417, 6251, 6667, 10417, 16667, 50001, 56251, 60417, 66667, 166667, 260417, 406251, 500001, 666667, 760417, 906251, 1406251, 1666667, 5000001, 5260417, 6406251, 6666667, 16666667
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OFFSET

1,2


COMMENTS

Given any number in the sequence, if you remove one or more digits from the beginning you always get another number in the sequence. This makes it easy to find higher terms  just take an existing term and try adding a digit (with perhaps additional 0's) at the beginning. For example, to 6251 prepend 5 to get a 5digit term, or 40 or 90 to get a 6digit term.


LINKS

Table of n, a(n) for n=1..38.
Robert Munafo, Sequence A094534, Centered Hexamorphic, or Automorphic Hexagonal, Numbers
Cliff Pickover, Centered Hexamorphic Numbers.


FORMULA

10^(d1) <= n < 10^d; 3n(n1)+1 == n mod 10^d


EXAMPLE

417 is in the sequence because if n=417, 3n(n1)+1=520417, which ends in 417.


PROG

(PARI) isok(n) = {my(m = 3*n*(n1)+1); (m  n) % 10^#Str(n) == 0; } \\ Michel Marcus, Jun 21 2018


CROSSREFS

Cf. A003215, A003226.
Sequence in context: A045821 A262754 A115914 * A262106 A081632 A276907
Adjacent sequences: A094531 A094532 A094533 * A094535 A094536 A094537


KEYWORD

base,easy,nonn


AUTHOR

Robert Munafo, May 07 2004


EXTENSIONS

Name changed by Robert Dawson, Jun 20 2018


STATUS

approved



