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A122471
a(n)=7*a(n-1)-n for n> 0, a(0)=1.
0
1, 6, 40, 277, 1935, 13540, 94774, 663411, 4643869, 32507074, 227549508, 1592846545, 11149925803, 78049480608, 546346364242, 3824424549679, 26770971847737, 187396802934142, 1311777620538976, 9182443343772813
OFFSET
0,2
COMMENTS
From a quiz.
REFERENCES
K. Russell and P. Carter, Number Puzzles, W. Foulsham and Co. Ltd. (1993).
FORMULA
G.f.: -(((x-3)*x+1)/((x-1)^2*(7*x-1))). - Harvey P. Dale, Jun 15 2011
a(0)=1, a(1)=6, a(2)=40, a(n)=9*a(n-1)-15*a(n-2)+7*a(n-3). - Harvey P. Dale, Jun 15 2011
MATHEMATICA
RecurrenceTable[{a[0]==1, a[n]==7a[n-1]-n}, a[n], {n, 0, 20}] (* or *) LinearRecurrence[{9, -15, 7}, {1, 6, 40}, 31](* Harvey P. Dale, Jun 15 2011 *)
PROG
(PARI) a(n)=if(n>0, 7*a(n-1)-n, 1) for(n=0, 30, print1(a(n), ", "))
CROSSREFS
Sequence in context: A123357 A081016 A083426 * A178397 A090041 A069720
KEYWORD
nonn
AUTHOR
Herman Jamke (hermanjamke(AT)fastmail.fm), Sep 14 2006
STATUS
approved