

A254711


Pentagonal numbers (A000326) which are also centered square numbers (A001844).


3



1, 5, 145, 925, 28085, 179401, 5448301, 34802825, 1056942265, 6751568605, 205041351065, 1309769506501, 39776965164301, 254088532692545, 7716526200523285, 49291865572847185, 1496966305936352945, 9562367832599661301, 290403746825451948001
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OFFSET

1,2


LINKS



FORMULA

a(n) = a(n1)+194*a(n2)194*a(n3)a(n4)+a(n5).
G.f.: x*(x^4+4*x^354*x^2+4*x+1) / ((x1)*(x^214*x+1)*(x^2+14*x+1)).


EXAMPLE

145 is in the sequence because it is the 10th pentagonal number and the 9th centered square number.


PROG

(PARI) Vec(x*(x^4+4*x^354*x^2+4*x+1)/((x1)*(x^214*x+1)*(x^2+14*x+1)) + O(x^100))


CROSSREFS



KEYWORD

nonn,easy


AUTHOR



STATUS

approved



