This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A124052 Sum from 1 to n of all factors of primes less than n such that the power of any factor (p) never exceeds log(n) base p. 1
 1, 3, 12, 28, 168, 168, 1344, 2880, 9360, 9360, 112320, 112320, 1572480, 1572480, 1572480, 3249792, 58496256, 58496256, 1169925120, 1169925120, 1169925120, 1169925120, 28078202880, 28078202880, 145070714880, 145070714880 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n) > a(n-1) implies n is either a prime or the power of a prime. LINKS Seiichi Manyama, Table of n, a(n) for n = 1..2000 FORMULA a(n) = a(n-1)(1+n*(P-1)/(n-1)), if n is the power of any prime (P); a(n) = a(n-1), if n is not the power of any prime. EXAMPLE a(5)  = (1+2+4)*(1+3)*(1+5). a(6)  = a(5), since 6 is not a primepower. a(7)  = (1+2+4)*(1+3)*(1+5)*(1+7). a(8)  = (1+2+4+8)*(1+3)*(1+5)*(1+7). a(9)  = (1+2+4+8)*(1+3+9)*(1+5)*(1+7). a(10) = a(9) since 10 is not a primepower. CROSSREFS Cf. A000203, A034699. Sequence in context: A005995 A034503 A026557 * A215640 A104353 A001860 Adjacent sequences:  A124049 A124050 A124051 * A124053 A124054 A124055 KEYWORD nonn AUTHOR Timothy Frison (frison(AT)gmail.com), Nov 03 2006 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 February 15 16:25 EST 2019. Contains 320136 sequences. (Running on oeis4.)