The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A186340 a(n) = 2^A001840(n). 0
 1, 2, 4, 8, 32, 128, 512, 4096, 32768, 262144, 4194304, 67108864, 1073741824, 34359738368, 1099511627776, 35184372088832, 2251799813685248, 144115188075855872, 9223372036854775808, 1180591620717411303424, 151115727451828646838272 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS A factor in the Hankel transform A186339 of A186338. a(n)*a(n-4) = 2*a(n-1)*a(n-3) = a(n-1)*a(n-3) + c(n)*a(n-2)^2, where c(3*n+2) = 2, c(3*n) = c(3*n+1) = 1 for all n in Z. - Michael Somos, Oct 19 2018 LINKS Table of n, a(n) for n=0..20. FORMULA a(n)=2^floor((n+1)(n+2)/6). EXAMPLE G.f. = 1 + 2*x + 4*x^2 + 8*x^3 + 32*x^4 + 128*x^5 + 512*x^6 + ... - Michael Somos, Oct 19 2018 MATHEMATICA a[ n_] := 2^Quotient[ Binomial[n + 2, 2], 3]; (* Michael Somos, Oct 19 2018 *) PROG (PARI) {a(n) = 2^(binomial(n+2, 2)\3)}; /* Michael Somos, Oct 19 2018 */ CROSSREFS Cf. A058937. Sequence in context: A192008 A298989 A074406 * A228920 A064378 A191650 Adjacent sequences: A186337 A186338 A186339 * A186341 A186342 A186343 KEYWORD nonn,easy AUTHOR Paul Barry, Feb 18 2011 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified August 10 22:34 EDT 2024. Contains 375058 sequences. (Running on oeis4.)