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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A196788 a(n) is the first occurrence of n in A196697. 0
 1, 1805, 133, 2, 3, 4, 5, 13, 6, 9, 8, 10, 19, 16, 32, 24, 74, 30, 18, 60, 168, 20, 42, 90, 180, 210, 186, 408, 144, 1020, 1050, 900, 2520, 3348, 2850, 5520, 3390, 774, 5760 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(39+k) > 9594, for any k >= 1. It is getting much harder for n>39. It took the Mathematica program weeks to get the first 39 items. LINKS Table of n, a(n) for n=1..39. EXAMPLE A196697(1)=1, a(1)=1; A196697(2)=4, a(4)=2; ... A196697(1805)=2, a(2)=1805; (for any k<1805, A196697(k)<>2) MATHEMATICA b = 2; max = 39; Array[fa, max]; Do[ fa[k] = 0, {k, 1, max}]; filled = 0; i = 0; While[filled < max, i++; c1 = b^i; cs = {}; Do[c2 = b^j; cp = c1 + c2 + 1; If[PrimeQ[cp], cs = Union[cs, {cp}]]; cp = c1 + c2 - 1; If[PrimeQ[cp], cs = Union[cs, {cp}]]; cp = c1 - c2 + 1; If[PrimeQ[cp], cs = Union[cs, {cp}]]; cp = c1 - c2 - 1; If[PrimeQ[cp], cs = Union[cs, {cp}]], {j, 0, i - 1}]; ct = Length[cs]; If[ct <= max, If[fa[ct] == 0, fa[ct] = i; filled++]]]; Table[ fa[k], {k, 1, max}] CROSSREFS Cf. A196697. Sequence in context: A252676 A248063 A256027 * A252029 A250385 A345765 Adjacent sequences: A196785 A196786 A196787 * A196789 A196790 A196791 KEYWORD nonn,more AUTHOR Lei Zhou, Oct 06 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 September 27 17:53 EDT 2023. Contains 365714 sequences. (Running on oeis4.)