1,2

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

A. Fletcher, J. C. P. Miller, L. Rosenhead and L. J. Comrie, An Index of Mathematical Tables. Vols. 1 and 2, 2nd ed., Blackwell, Oxford and Addison-Wesley, Reading, MA, 1962, Vol. 1, p. 75.

Glaisher, J. W. L., Quart. J. Pure Appl. Math., 44 (1913), 105-112.

4^n * A000364(n).

A := n -> (-4)^n*euler(2*n); (Then A(n) = a(n+1) for n >= 0.) [From Peter Luschny (peter(AT)luschny.de), Jan 27 2009]

(PARI) a(n)=if(n<0, 0, 4^n*(2*n)!*polcoeff(1/cos(x+O(x^(2*n+1))), 2*n))

Cf. A002436(n)=A000831(2n).

Equals 2 * A000816(n-1), n>1.

Sequence in context: A012824 A012057 A102063 this_sequence A013031 A012923 A012922

Adjacent sequences: A002433 A002434 A002435 this_sequence A002437 A002438 A002439

nonn,easy,nice

N. J. A. Sloane (njas(AT)research.att.com).

More terms from Michael Somos, Jun 21, 2002