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A244472 2nd-largest term in n-th row of Stern's diatomic triangle A002487. 5
1, 2, 4, 7, 12, 19, 31, 50, 81, 131, 212, 343, 555, 898, 1453, 2351, 3804, 6155, 9959, 16114, 26073, 42187, 68260, 110447, 178707, 289154, 467861, 757015, 1224876, 1981891, 3206767, 5188658, 8395425, 13584083, 21979508, 35563591, 57543099 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Colin Barker, Table of n, a(n) for n = 1..1000

Jennifer Lansing, Largest Values for the Stern Sequence, J. Integer Seqs., 17 (2014), #14.7.5.

Index entries for linear recurrences with constant coefficients, signature (1,1).

FORMULA

a(n) = A013655(n-1), n>3.

a(n) = a(n-1)+a(n-2), n>5. - Colin Barker, Jul 10 2015

G.f.: -x*(x^4+x^3+x^2+x+1) / (x^2+x-1). - Colin Barker, Jul 10 2015

MAPLE

A244472 := proc(n)

    if n < 4 then

        op(n, [1, 2, 4]) ;

    else

        combinat[fibonacci](n+2)-combinat[fibonacci](n-3) ;

    end if;

end proc:

seq(A244472(n), n=1..50) ; # R. J. Mathar, Jul 05 2014

MATHEMATICA

CoefficientList[Series[-(x^4 + x^3 + x^2 + x + 1)/(x^2 + x - 1), {x, 0, 50}], x] (* Wesley Ivan Hurt, Jul 10 2015 *)

Join[{1, 2, 4}, LinearRecurrence[{1, 1}, {7, 12}, 50]] (* Vincenzo Librandi, Jul 11 2015 *)

PROG

(PARI) Vec(-x*(x^4+x^3+x^2+x+1)/(x^2+x-1) + O(x^100)) \\ Colin Barker, Jul 10 2015

(MAGMA) I:=[1, 2, 4, 7, 12]; [n le 5 select I[n] else Self(n-1)+Self(n-2): n in [1..40]]; // Wesley Ivan Hurt, Jul 10 2015

CROSSREFS

Cf. A002487, A013655, A100545 (bisection).

Cf. A244473, A244474, A244475, A244476.

Sequence in context: A342229 A326080 A287525 * A279890 A018147 A125892

Adjacent sequences:  A244469 A244470 A244471 * A244473 A244474 A244475

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Jul 01 2014

STATUS

approved

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Last modified September 21 16:31 EDT 2021. Contains 347598 sequences. (Running on oeis4.)