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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A336997 a(n) = n! * Sum_{d|n} 2^(d - 1) / d!. 1
 1, 4, 10, 56, 136, 1952, 5104, 94208, 605056, 7741952, 39917824, 1458295808, 6227024896, 175463616512, 2353813878784, 48886264659968, 355687428161536, 17362063156969472, 121645100409094144, 6001501553433509888, 85800344155030552576, 2248030289949388439552 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS FORMULA E.g.f.: Sum_{k>=1} (exp(2*x^k) - 1) / 2. a(p) = p! + 2^(p - 1), where p is prime. MATHEMATICA Table[n! Sum[2^(d - 1)/d!, {d, Divisors[n]}], {n, 1, 22}] nmax = 22; CoefficientList[Series[Sum[(Exp[2 x^k] - 1)/2, {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]! // Rest PROG (PARI) a(n) = n! * sumdiv(n, d, 2^(d-1)/d!); \\ Michel Marcus, Aug 12 2020 CROSSREFS Cf. A010842, A034729, A057625, A336998. Sequence in context: A013589 A225543 A002290 * A222569 A348514 A254078 Adjacent sequences:  A336994 A336995 A336996 * A336998 A336999 A337000 KEYWORD nonn AUTHOR Ilya Gutkovskiy, Aug 10 2020 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 June 28 12:59 EDT 2022. Contains 354907 sequences. (Running on oeis4.)