This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A105348 An indicator sequence for the Jacobsthal numbers. 9
 1, 2, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS a(n) is the number of solutions to the Diophantine equation 2*x^2 - (9*n+1)*x + 9*n^2 = 1 where valid solutions are restricted to powers of 4. - Hieronymus Fischer, May 17 2007 LINKS Antti Karttunen, Table of n, a(n) for n = 0..87381 FORMULA G.f.: Sum_{k>=0} x^A001045(k). a(n) = 1 + floor(log_2(3n+1)) - ceiling(log_2(3n-1)) = floor(log_2(3n+1)) - floor(log_2(3n-2)) for n >= 1. Also true: a(n) = 1 + A130249(n) - A130250(n) = A130253(n) - A130250(n) = A130250(n+1) - A130250(n) for n >= 0. - Hieronymus Fischer, May 17 2007 EXAMPLE a(1)=2 since J(1)=J(2)=1. PROG (PARI) A147612aux(n, i) = if(!(n%2), n, A147612aux((n+i)/2, -i)); A147612(n) = 0^(A147612aux(n, 1)*A147612aux(n, -1)); A105348(n) = if(1==n, 2, A147612(n)); \\ Antti Karttunen, Nov 02 2018 CROSSREFS For partial sums see A130253. Cf. A130249, A130250, A147612. Sequence in context: A237996 A203951 A323591 * A016406 A129182 A116857 Adjacent sequences:  A105345 A105346 A105347 * A105349 A105350 A105351 KEYWORD easy,nonn AUTHOR Paul Barry, Apr 01 2005 STATUS approved

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

Last modified October 19 16:17 EDT 2019. Contains 328223 sequences. (Running on oeis4.)