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A126019
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a(0)=1, a(1)=2; for n>1, a(n)=3*a(n-1)+4*a(n-2)+5.
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0
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1, 2, 15, 58, 239, 954, 3823, 15290, 61167, 244666, 978671, 3914682, 15658735, 62634938, 250539759, 1002159034, 4008636143, 16034544570, 64138178287, 256552713146, 1026210852591, 4104843410362, 16419373641455, 65677494565818
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OFFSET
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0,2
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COMMENTS
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First prime terms are a(n) with a = 1, 4, 6, 18, 88.
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LINKS
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FORMULA
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a(n) = (28*4^n + 27(-1)^n - 25)/30.
G.f. = (1 - 2*x + 6*x^2)/(1 - 4*x - x^2 + 4*x^3).
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MATHEMATICA
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RecurrenceTable[{a[0]==1, a[1]==2, a[n]==3a[n-1]+4a[n-2]+5}, a, {n, 30}] (* Harvey P. Dale, May 30 2020 *)
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PROG
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(Sage)
from sage.combinat.sloane_functions import recur_gen2b
it = recur_gen2b(1, 2, 3, 4, lambda n: 5)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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