This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A278165 Least number with the prime signature of the n-th Jacobsthal number. 5
 1, 1, 2, 2, 2, 6, 2, 6, 12, 6, 2, 210, 2, 6, 30, 30, 2, 420, 2, 420, 30, 30, 2, 30030, 30, 6, 120, 2310, 6, 30030, 2, 210, 210, 6, 210, 19399380, 6, 6, 30, 60060, 6, 60060, 2, 30030, 4620, 30, 6, 223092870, 6, 30030, 2310, 30030, 6, 120120, 420, 510510, 210, 2310, 30, 401120980260, 2, 6, 4620, 30030, 2310, 9699690, 6, 30030, 210, 9699690, 6, 14841476269620, 6 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Antti Karttunen (terms 1..257) & Hans Havermann, Table of n, a(n) for n = 1..1032 FORMULA a(n) = A046523(A001045(n)). MATHEMATICA Table[Times @@ MapIndexed[(Prime@ First@ #2)^#1 &, #] &@ If[Length@# == 1 && #[[1, 1]] == 1, {0}, Reverse@ Sort@ #[[All, -1]]] &@ FactorInteger[ (2^n - (-1)^n)/3], {n, 120}] (* Michael De Vlieger, Nov 21 2016 *) PROG (PARI) A001045(n) = (2^n - (-1)^n) / 3; A046523(n) = my(f=vecsort(factor(n)[, 2], , 4), p); prod(i=1, #f, (p=nextprime(p+1))^f[i]) \\ From Charles R Greathouse IV, Aug 17 2011 A278165(n) = A046523(A001045(n)); for(n=1, 257, write("b278165.txt", n, " ", A278165(n))); (Scheme) (define (A278165 n) (A046523 (A001045 n))) CROSSREFS Cf. A001045, A046523. Cf. A107036 (positions of 2's), A286565 (rgs-version of this sequence). Cf. also A278245, A278248, A278258, A286567. Sequence in context: A291439 A023957 A224964 * A074928 A285713 A278230 Adjacent sequences:  A278162 A278163 A278164 * A278166 A278167 A278168 KEYWORD nonn AUTHOR Antti Karttunen, Nov 19 2016 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 August 22 02:44 EDT 2019. Contains 326169 sequences. (Running on oeis4.)