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 A161849 a(n) = A052369(n) mod A056608(n). 5
 0, 1, 0, 0, 1, 1, 1, 2, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 0, 2, 1, 2, 1, 1, 1, 1, 1, 1, 2, 1, 1, 0, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 3, 1, 1, 2, 1, 1, 1, 2, 1, 4, 1, 1, 0, 1, 1, 2, 1, 2, 1, 1, 6, 1, 1, 1, 4, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 3, 1, 0, 1, 2, 1, 0, 1, 0, 1, 1, 1, 5, 1, 2, 1, 1, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,8 COMMENTS (Largest prime divisor) modulo (smallest prime divisor) of n-th composite number. LINKS Table of n, a(n) for n=1..105. EXAMPLE a(1) = 0 = 2 mod 2; a(2) = 1 = 3 mod 2; a(3) = 0 = 2 mod 2; a(4) = 0 = 3 mod 3; a(5) = 1 = 5 mod 2. MAPLE A002808 := proc(n) option remember; local a; if n = 1 then 4; else for a from procname(n-1)+1 do if not isprime(a) then RETURN(a) : fi; od: fi; end: A006530 := proc(n) local u: if n=1 then 1 else u:= numtheory[factorset](n): max(seq(u[j], j=1..nops(u))) end if end: A020639 := proc(n) local u: if n=1 then 1 else u:= numtheory[factorset](n): min(seq(u[j], j=1..nops(u))) end if end: A052369 := proc(n) A006530(A002808(n)) ; end: A056608 := proc(n) A020639(A002808(n)) ; end: A161849 := proc(n) A052369(n) mod A056608(n) ; end: seq(A161849(n), n=1..120) ; # R. J. Mathar, Jun 23 2009 MATHEMATICA Composite[n_] := FixedPoint[n + PrimePi[#] + 1&, n + PrimePi[n] + 1]; a[n_] := With[{f = FactorInteger[Composite[n]]}, f[[-1, 1]]~Mod~f[[1, 1]]]; Table[a[n], {n, 1, 105}] (* Jean-François Alcover, Oct 15 2023 *) PROG (Magma) [ D[ #D] mod D[1]: n in [2..140] | not IsPrime(n) where D is PrimeDivisors(n) ]; // Klaus Brockhaus, Jun 24 2009 CROSSREFS Cf. A052369, A056608, A002808. Cf. A161850, A161986. - Klaus Brockhaus, Jun 24 2009 Sequence in context: A236575 A059282 A114591 * A056175 A325987 A359324 Adjacent sequences: A161846 A161847 A161848 * A161850 A161851 A161852 KEYWORD nonn AUTHOR Juri-Stepan Gerasimov, Jun 20 2009 EXTENSIONS a(102) corrected by R. J. Mathar, Jun 23 2009 STATUS approved

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Last modified July 25 00:10 EDT 2024. Contains 374585 sequences. (Running on oeis4.)