

A190322


a(1) = 1, a(2) = 9, a(3) = 17; for n>3, a(n) = a(n3) + 2.


2



1, 9, 17, 3, 11, 19, 5, 13, 21, 7, 15, 23, 9, 17, 25, 11, 19, 27, 13, 21, 29, 15, 23, 31, 17, 25, 33, 19, 27, 35, 21, 29, 37, 23, 31, 39, 25, 33, 41, 27, 35, 43, 29, 37, 45, 31, 39, 47, 33, 41, 49, 35, 43, 51, 37, 45, 53, 39, 47, 55, 41, 49, 57, 43, 51, 59
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OFFSET

1,2


REFERENCES

Clifford A. Pickover, A Passion for Mathematics, Wiley, 2005; see p. 62.


LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (1,0,1,1).


FORMULA

a(1)=1, a(2)=9, a(3)=17, a(4)=3, a(n) = a(n1)+a(n3)a(n4).  Harvey P. Dale, Feb 24 2014
G.f.: x*(1+8*x+8*x^215*x^3) / ((x1)^2*(x^2+x+1)).  Colin Barker, Sep 12 2014


MATHEMATICA

RecurrenceTable[{a[1]==1, a[2]==9, a[3]==17, a[n]==a[n3]+2}, a, {n, 70}] (* or *) LinearRecurrence[{1, 0, 1, 1}, {1, 9, 17, 3}, 70] (* Harvey P. Dale, Feb 24 2014 *)


PROG

(PARI) Vec(x*(15*x^38*x^28*x1)/((x1)^2*(x^2+x+1)) + O(x^100)) \\ Colin Barker, Sep 12 2014
(MAGMA) I:=[1, 9, 17, 3]; [n le 4 select I[n] else Self(n1)+Self(n3)Self(n4): n in [1..30]]; // G. C. Greubel, Dec 30 2017


CROSSREFS

Cf. A136313.
Sequence in context: A050802 A264519 A136313 * A184938 A103707 A271641
Adjacent sequences: A190319 A190320 A190321 * A190323 A190324 A190325


KEYWORD

nonn,easy


AUTHOR

Nathaniel Johnston, May 08 2011


STATUS

approved



