A050686 - OEIS

A050686

Number of palindromes of length n and containing the digit 1 (or any other fixed nonzero digit).

1, 1, 18, 18, 252, 252, 3168, 3168, 37512, 37512, 427608, 427608, 4748472, 4748472, 51736248, 51736248, 555626232, 555626232, 5900636088, 5900636088, 62105724792, 62105724792, 648951523128, 648951523128, 6740563708152

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OFFSET

1,3

LINKS

Table of n, a(n) for n=1..25.

FORMULA

Empirical g.f.: -x*(x-1)*(x+1)^2 / ((3*x-1)*(3*x+1)*(10*x^2-1)). [Colin Barker, Feb 15 2013]

EXAMPLE

For length 3 we find 18 numbers: 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 212, 313, 414, 515, 616, 717, 818, 919.

CROSSREFS

Cf. A050683, A050720.

Sequence in context: A298378 A299245 A352365 * A165839 A372457 A177014

Adjacent sequences: A050683 A050684 A050685 * A050687 A050688 A050689

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, Aug 15 1999

EXTENSIONS

More terms from Michael Lugo (mlugo(AT)thelabelguy.com), Dec 22 1999

STATUS

approved