This site is supported by donations to The OEIS Foundation. Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A120318 Consecutive refactorable numbers a(n)-1, a(n) in which 11 is the smallest prime divisor of a(n). 0
 38604666779024731098340977806401, 7208577773559712596404976530284801, 695314235787112476661749457231833601, 313468146036745542621075945985861000534849 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS FORMULA a(n) is the first integer of the form (11*k)^(11-1) such that both a(n) and a(n)-1 is refactorable and 11 is the smallest prime divisor of a(n). MAPLE with(numtheory); RFC11:=[]: p:=ithprime(5): P:=[seq(ithprime(i), i=1..4)]; for w to 1 do for k from 3 to 12^4 by 2 do if andmap(z -> k mod z <> 0, P) then m:=p*k; n:=m^(p-1); t:=tau(n); n1:=n-1; t1:=tau(n1); if (n mod t = 0) and (n1 mod t1 = 0) then RFC11:=[op(RFC11), n]; print(ifactor(n)); fi fi; od od; CROSSREFS Cf. A033950, A036898, A114617. Sequence in context: A104319 A003943 A003936 * A095458 A277140 A083104 Adjacent sequences:  A120315 A120316 A120317 * A120319 A120320 A120321 KEYWORD nonn AUTHOR Walter Kehowski, Jun 20 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 October 15 05:43 EDT 2019. Contains 328026 sequences. (Running on oeis4.)