This site is supported by donations to The OEIS Foundation. Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A294639 a(n) = least prime p such that n divides p + prime(n). 1
 2, 3, 7, 5, 19, 5, 11, 5, 13, 11, 2, 11, 11, 13, 13, 11, 43, 11, 47, 29, 11, 31, 101, 7, 3, 3, 5, 5, 7, 7, 59, 29, 61, 31, 61, 29, 139, 103, 67, 67, 67, 29, 67, 71, 73, 31, 71, 17, 67, 71, 73, 73, 607, 19, 73, 17, 73, 19, 313, 19, 83, 17, 71, 73, 337, 13, 71 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS This sequence was inspired by A134204. The logarithmic scatterplot of the sequence has interesting features (see Links section). We observe runs of consecutive equal terms: - first pair: a(12) = a(13) = 11, - first triple: a(39) = a(40) = a(41) = 67, - first quadruple: a(24980) = a(24981) = a(24982) = a(24983) = 12983. a(1) = prime(1). a(2) = prime(2). LINKS Rémy Sigrist, Table of n, a(n) for n = 1..10000 Rémy Sigrist, Logarithmic scatterplot of the sequence for n=1..50000 Rémy Sigrist, Colored logarithmic scatterplot of the sequence for n=1..50000 (where the color is function of (a(n) + prime(n))/n) EXAMPLE For n=3: - prime(3) = 5, - 3 does not divide 2 + 5, - 3 does not divide 3 + 5, - 3 does not divide 5 + 5, - 3 divides 7 + 5, - hence a(3) = 7. MAPLE P:=proc(n) local k; k:=1; while ithprime(k)+ithprime(n) mod n>0 do k:=k+1; od; ithprime(k); end: seq(P(i), i=1..10^2); # Paolo P. Lava, Nov 17 2017 PROG (PARI) a(n) = my (q=prime(n)); forprime(p=2, , if ((p+q)%n==0, return (p))) CROSSREFS Cf. A134204, A254862. Sequence in context: A228775 A129543 A137440 * A038026 A051860 A155766 Adjacent sequences:  A294636 A294637 A294638 * A294640 A294641 A294642 KEYWORD nonn,look AUTHOR Rémy Sigrist, Nov 05 2017 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 July 23 20:55 EDT 2019. Contains 325264 sequences. (Running on oeis4.)