

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
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OFFSET

0,4


COMMENTS

a(n) is the number of palindromic word structures of length n using 10ary 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 10ary 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

Fourdigit 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



