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 A329605 Number of divisors of A108951(n), where A108951 is fully multiplicative with a(prime(i)) = prime(i)# = Product_{i=1..i} A000040(i). 16
 1, 2, 4, 3, 8, 6, 16, 4, 9, 12, 32, 8, 64, 24, 18, 5, 128, 12, 256, 16, 36, 48, 512, 10, 27, 96, 16, 32, 1024, 24, 2048, 6, 72, 192, 54, 15, 4096, 384, 144, 20, 8192, 48, 16384, 64, 32, 768, 32768, 12, 81, 36, 288, 128, 65536, 20, 108, 40, 576, 1536, 131072, 30, 262144, 3072, 64, 7, 216, 96, 524288, 256, 1152, 72, 1048576, 18, 2097152, 6144, 48 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Antti Karttunen, Table of n, a(n) for n = 1..10000 FORMULA a(n) = A000005(A108951(n)). a(n) >= A329382(n) >= A329617(n) >= A329378(n). A020639(a(n)) = A329614(n). From Antti Karttunen, Jan 14 2020: (Start) a(A052126(n)) = A329382(n). a(A002110(n)) = A000142(1+n), for all n >= 0. a(n) > A056239(n). a(A329902(n)) = A002183(n). A000265(a(n)) = A331286(n). gcd(n,a(n)) = A331283(n). If n = p(k1)^e(k1) * p(k2)^e(k2) * p(k3)^e(k3) * ... * p(kx)^e(kx), with p(n) = A000040(n) and k1 > k2 > ... > kx, then a(n) = (1+e(k1))^(k1-k2) * (1+e(k1)+e(k2))^(k2-k3) * ... * (1+e(k1)+e(k2)+...+e(kx))^kx. A000035(a(n)) = A000035(A000005(n)) = A010052(n). (End) MATHEMATICA Block[{a}, a[n_] := a[n] = Module[{f = FactorInteger[n], p, e}, If[Length[f] > 1, Times @@ a /@ Power @@@ f, {{p, e}} = f; Times @@ (Prime[Range[PrimePi[p]]]^e)]]; a[1] = 1; Array[DivisorSigma[0, a@ #] &, 75]] (* Michael De Vlieger, Jan 24 2020, after Jean-François Alcover at A108951 *) PROG (PARI) A034386(n) = prod(i=1, primepi(n), prime(i)); A108951(n) = { my(f=factor(n)); prod(i=1, #f~, A034386(f[i, 1])^f[i, 2]) };  \\ From A108951 A329605(n) = numdiv(A108951(n)); (PARI) A329605(n) = if(1==n, 1, my(f=factor(n), e=1, m=1); forstep(i=#f~, 1, -1, e += f[i, 2]; m *= e^(primepi(f[i, 1])-if(1==i, 0, primepi(f[i-1, 1])))); (m)); \\ Antti Karttunen, Jan 14 2020 (PARI) A329605(n) = if(1==n, 1, my(f=factor(n), e=0, d); forstep(i=#f~, 1, -1, e += f[i, 2]; d = (primepi(f[i, 1])-if(1==i, 0, primepi(f[i-1, 1]))); f[i, 1] = (e+1); f[i, 2] = d); factorback(f)); \\ Antti Karttunen, Jan 14 2020 CROSSREFS Cf. A000005, A000040, A000142, A002110, A010052, A034386, A052126, A056239, A108951, A329902, A329378, A329382, A329614, A329617, A331283, A331286 (odd part). Cf. A329606 (rgs-transform), A329608, A331284 (ordinal transform). Cf. A331285 (the position where for the first time some term has occurred n times in this sequence). Sequence in context: A243072 A243346 A295029 * A243073 A243345 A297499 Adjacent sequences:  A329602 A329603 A329604 * A329606 A329607 A329608 KEYWORD nonn AUTHOR Antti Karttunen, Nov 18 2019 STATUS approved

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Last modified August 11 00:32 EDT 2020. Contains 336403 sequences. (Running on oeis4.)