login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A164904 a(n) is the number of palindromic structures using a maximum of ten different symbols. 3
1, 1, 1, 2, 2, 5, 5, 15, 15, 52, 52, 203, 203, 877, 877, 4140, 4140, 21147, 21147, 115975, 115975, 678569, 678569, 4213530, 4213530, 27641927, 27641927, 190829797, 190829797, 1381367941, 1381367941, 10448276360, 10448276360, 82285618467 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

a(n) is the number of palindromic word structures of length n using 10-ary alphabet. a(n) is the same as taking every element twice from A164864 - Number of ways of placing n labeled balls into 10 indistinguishable boxes; word structures of length n using a 10-ary alphabet.

LINKS

Table of n, a(n) for n=0..33.

Index entries for linear recurrences with constant coefficients, signature (1, 45, -45, -861, 861, 9135, -9135, -58674, 58674, 233100, -233100, -557864, 557864, 732960, -732960, -403200, 403200).

FORMULA

G.f.: (148329*x^17 -403200*x^16 -210253*x^15 +732960*x^14 +122692*x^13 -557864*x^12 -38365*x^11 +233100*x^10 +6965*x^9 -58674*x^8 -736*x^7 +9135*x^6 +42*x^5 -861*x^4 -x^3 +45*x^2 -1) / ((x -1)*(2*x -1)*(2*x +1)*(2*x^2 -1)*(3*x^2 -1)*(5*x^2 -1)*(6*x^2 -1)*(7*x^2 -1)*(8*x^2 -1)*(10*x^2 -1)). [Colin Barker, Dec 05 2012]

EXAMPLE

Four-digit palindromes have two different digits structures: aaaa and abba. Hence a(4)=2.

CROSSREFS

Cf. A056470, A056471, A164864, A188164

Sequence in context: A055879 A056470 A056471 * A188164 A245846 A245847

Adjacent sequences:  A164901 A164902 A164903 * A164905 A164906 A164907

KEYWORD

nonn,easy

AUTHOR

Tanya Khovanova, Aug 30 2009

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 5 03:59 EST 2021. Contains 349530 sequences. (Running on oeis4.)