This site is supported by donations to The OEIS Foundation.

 Annual appeal: Please make a donation to keep the OEIS running! Over 6000 articles have referenced us, often saying "we discovered this result with the help of the OEIS". Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A061898 Swap each prime in factorization of n with "neighbor" prime. 5
 1, 3, 2, 9, 7, 6, 5, 27, 4, 21, 13, 18, 11, 15, 14, 81, 19, 12, 17, 63, 10, 39, 29, 54, 49, 33, 8, 45, 23, 42, 37, 243, 26, 57, 35, 36, 31, 51, 22, 189, 43, 30, 41, 117, 28, 87, 53, 162, 25, 147, 38, 99, 47, 24, 91, 135, 34, 69, 61, 126, 59, 111, 20, 729, 77, 78, 71, 171, 58 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Here "neighbor" primes are just paired in order: 2<->3, 5<->7, 11<->13, etc. Self-inverse permutation of the integers. Multiplicative. LINKS Alois P. Heinz, Table of n, a(n) for n = 1..20000 EXAMPLE a(60)=126 since 60=2^2*3*5, swapping 2<->3 and 5<->7 gives 3^2*2*7=126 (and of course then a(126)=60). MAPLE p:= proc(n) option remember; `if`(numtheory[pi](n)::odd,        nextprime(n), prevprime(n))     end: a:= n-> mul(p(i[1])^i[2], i=ifactors(n)[2]): seq(a(n), n=1..80);  # Alois P. Heinz, Sep 13 2017 PROG (PARI) a(n) = my(f=factor(n)); for (i=1, #f~, ip = primepi(f[i, 1]); if (ip % 2, f[i, 1] = prime(ip+1), f[i, 1] = prime(ip-1))); factorback(f); \\ Michel Marcus, Jun 09 2014 CROSSREFS Cf. A045965. Sequence in context: A227630 A286251 A072027 * A021756 A274925 A084398 Adjacent sequences:  A061895 A061896 A061897 * A061899 A061900 A061901 KEYWORD easy,nonn,mult AUTHOR Marc LeBrun, May 14 2001 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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.