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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A285102 a(n) = A007913(A285101(n)). 6
 2, 6, 210, 72930, 620310, 278995269860970, 12849025509071310, 492608110538467706074890, 1342951001046021018427857601026746070, 37793589449865555275592120894959094883390892772270, 728982633030274864467458719371654181886452163442582606072870, 28339554655955912942523491885490197708224606885407444005070 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 LINKS Table of n, a(n) for n=0..11. FORMULA a(0) = 2, for n > 0, a(n) = lcm(a(n-1),A242378(n,a(n-1))) / gcd(a(n-1),A242378(n,a(n-1))). a(n) = A007913(A285101(n)). Other identities. For all n >= 0: A001221(a(n)) = A001222(a(n)) = A285103(n). A048675(a(n)) = A068052(n). PROG (PARI) A003961(n) = { my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); }; A242378(k, n) = { while(k>0, n = A003961(n); k = k-1); n; }; A285102(n) = { if(0==n, 2, lcm(A285102(n-1), A242378(n, A285102(n-1)))/gcd(A285102(n-1), A242378(n, A285102(n-1)))); }; (Scheme) (definec (A285102 n) (if (zero? n) 2 (/ (lcm (A285102 (- n 1)) (A242378bi n (A285102 (- n 1)))) (gcd (A285102 (- n 1)) (A242378bi n (A285102 (- n 1))))))) (Python) # uses [A003961, A242378] from sympy import factorint, prime, primepi from sympy.ntheory.factor_ import core from operator import mul def a003961(n): f=factorint(n) return 1 if n==1 else reduce(mul, [prime(primepi(i) + 1)**f[i] for i in f]) def a242378(k, n): while k>0: n=a003961(n) k-=1 return n l=[2] for n in range(1, 12): x=l[n - 1] l.append(x*a242378(n, x)) print([core(j) for j in l]) # Indranil Ghosh, Jun 27 2017 CROSSREFS Cf. A003961, A007913, A048675, A068052, A242378, A285101, A285103. Sequence in context: A156517 A333944 A091439 * A285101 A361086 A176782 Adjacent sequences: A285099 A285100 A285101 * A285103 A285104 A285105 KEYWORD nonn AUTHOR Antti Karttunen, Apr 15 2017 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 September 29 00:22 EDT 2023. Contains 365739 sequences. (Running on oeis4.)