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A075681 Difference between (n-1)*(n-2)^3 and A003878(n). 3
0, 0, 2, 21, 60, 121, 207, 321, 466, 645, 861, 1117, 1416, 1761, 2155, 2601, 3102, 3661, 4281, 4965, 5716, 6537, 7431, 8401, 9450, 10581, 11797, 13101, 14496, 15985, 17571, 19257, 21046, 22941, 24945, 27061, 29292, 31641, 34111, 36705 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..40.

Ed Pegg Jr., Pancakes

FORMULA

a(n) = 1/2*n^3+7/2*n^2-23n+25, for n>3. G.f.: (x^7-x^6-12x^5+13x^4+2x^3)/(1-x)^4. - Ralf Stephan, Mar 13 2003

EXAMPLE

4 gives 3*2*2*2=24. Prefix flips involving 4 flips give 3, hence a[4]=24-3=21.

MAPLE

A075681:=n->1/2*n^3+7/2*n^2-23*n+25: (0, 0, 2, seq(A075681(n), n=4..50)); # Wesley Ivan Hurt, Sep 06 2015

MATHEMATICA

CoefficientList[Series[x^2 (x^4 - x^3 - 12 x^2 + 13 x + 2)/(1 - x)^4, {x, 0, 40}], x] (* Vincenzo Librandi, Sep 07 2015 *)

PROG

(MAGMA) [0, 0, 2] cat [1/2*n^3+7/2*n^2-23*n+25: n in [4..50]]; // Vincenzo Librandi, Sep 07 2015

CROSSREFS

Cf. A003878.

Sequence in context: A231807 A097718 A180232 * A212257 A034520 A111128

Adjacent sequences:  A075678 A075679 A075680 * A075682 A075683 A075684

KEYWORD

nonn,easy

AUTHOR

Jon Perry, Oct 12 2002

EXTENSIONS

More terms from Ralf Stephan, Mar 13 2003

STATUS

approved

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Last modified September 23 02:41 EDT 2021. Contains 347609 sequences. (Running on oeis4.)