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1, 2, 2, 3, 4, 4, 3, 4, 5, 5, 6, 6, 6, 6, 4, 5, 6, 6, 8, 9, 10, 9, 8, 8, 8, 8, 9, 9, 8, 8, 5, 6, 7, 7, 10, 10, 13, 13, 11, 12, 13, 12, 15, 16, 14, 13, 10, 10, 10, 10, 13, 14, 15, 14, 12, 12, 11, 11, 12, 12, 10, 10, 6, 7, 8, 8, 12, 12, 15, 15, 14, 15, 17, 17, 20, 21, 20, 19, 14, 15, 16, 15, 21, 22, 24, 24, 20, 21, 20, 18, 21, 21, 17, 17, 12, 12, 12, 12, 17, 18
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internal format)
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OFFSET
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0,2
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LINKS
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FORMULA
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Other identities. For all n >= 0:
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MATHEMATICA
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a[p_?PrimeQ] := a[p] = Prime[ PrimePi[p] + 1]; a[1] = 1; a[n_] := a[n] = Times @@ ( a[First[#]] ^ Last[#] & ) /@ FactorInteger[n]; (* after Jean-François Alcover, in A003961 *) A[n_]:= If[n<2, n + 1, If[EvenQ[n], a[A[n/2]], A[(n - 1)/2] A[(n + 1)/2]]] ; Table[A[n], {n, 0, 51}] (* sequence A260443 *) Table[PrimeOmega[LCM[A[n], A[n + 1]]], {n, 0, 101}] (* Indranil Ghosh, Mar 22 2017 *)
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PROG
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(PARI)
A003961(n) = my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); \\ From Michel Marcus
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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