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A276055 Number of palindromic compositions of n with parts in {1,2,4,6,8,10,...}. 2
1, 1, 2, 1, 4, 2, 7, 3, 13, 6, 23, 10, 42, 19, 75, 33, 136, 61, 244, 108, 441, 197, 793, 352, 1431, 638, 2576, 1145, 4645, 2069, 8366, 3721, 15080, 6714, 27167, 12087, 48961, 21794, 88215, 39254, 158970, 70755, 286439, 127469, 516164, 229725, 930072 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

REFERENCES

S. Heubach and T. Mansour, Combinatorics of Compositions and Words, CRC Press, 2010.

LINKS

Table of n, a(n) for n=0..46.

V. E. Hoggatt, Jr., and Marjorie Bicknell, Palindromic compositions, Fibonacci Quart., Vol. 13(4), 1975, pp. 350-356.

FORMULA

G.f.: g(z) =(1+z^2 )*(1+z-z^3)/(1-z^2-2z^4+z^6). In the more general situation of compositions into a[1]<a[2]<a[3]<..., denoting F(z) = Sum(z^{a[j]},j>=1}, we have g(z)=(1+F(z))/(1-F(z^2)) (see Theorem 1.2 in the Hoggatt et al. reference).

EXAMPLE

a(6) = 7 because the palindromic compositions of 6 with parts in {1,2,4,6,8,...} are 6, 141, 222, 2112, 1221, 11211, and 111111.

MAPLE

g := (1+z^2)*(1+z-z^3)/(1-z^2-2*z^4+z^6): gser:= series(g, z=0, 55): seq(coeff(gser, z, n), n=0..50);

MATHEMATICA

CoefficientList[Series[(1 + x^2) (1 + x - x^3)/(1 - x^2 - 2 x^4 + x^6), {x, 0, 50}], x] (* Vincenzo Librandi, Aug 18 2016 *)

CROSSREFS

Cf. A028495, A276053,

Sequence in context: A143375 A074364 A256610 * A252866 A008796 A254594

Adjacent sequences:  A276052 A276053 A276054 * A276056 A276057 A276058

KEYWORD

nonn

AUTHOR

Emeric Deutsch, Aug 17 2016

STATUS

approved

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Last modified December 7 05:14 EST 2019. Contains 329839 sequences. (Running on oeis4.)