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A061165
Polynomial extrapolation of 2, 3, 5, 7, 11.
2
2, 3, 5, 7, 11, 22, 48, 100, 192, 341, 567, 893, 1345, 1952, 2746, 3762, 5038, 6615, 8537, 10851, 13607, 16858, 20660, 25072, 30156, 35977, 42603, 50105, 58557, 68036, 78622, 90398, 103450, 117867, 133741, 151167, 170243, 191070, 213752
OFFSET
1,1
FORMULA
a(n) = (3n^4-34n^3+141n^2-206n+144)/24.
G.f.: x*(2-7*x+10*x^2-8*x^3+6*x^4)/(1-x)^5. [Colin Barker, Mar 28 2012]
a(1)=2, a(2)=3, a(3)=5, a(4)=7, a(5)=11, a(n)=5*a(n-1)-10*a(n-2)+ 10*a(n-3)- 5*a(n-4)+a(n-5). - Harvey P. Dale, Oct 05 2012
EXAMPLE
a(6)=22 since first differences of (2,3,5,7,11) are (1,2,2,4), second differences (1,0,2), third differences (-1,2) and fourth differences (3), so a(6)=11+4+2+2+3=22.
MATHEMATICA
Table[(3n^4-34n^3+141n^2-206n+144)/24, {n, 40}] (* or *) LinearRecurrence[ {5, -10, 10, -5, 1}, {2, 3, 5, 7, 11}, 40] (* Harvey P. Dale, Oct 05 2012 *)
PROG
(PARI) for (n=1, 1000, write("b061165.txt", n, " ", (3*n^4 - 34*n^3 + 141*n^2 - 206*n + 144)/24)) \\ Harry J. Smith, Jul 18 2009
CROSSREFS
Cf. A061166.
Sequence in context: A038204 A075049 A361820 * A183055 A046689 A048278
KEYWORD
nonn,easy
AUTHOR
Henry Bottomley, Apr 18 2001
STATUS
approved