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 A064924 If n is prime then a(n) = n; for the subsequent nonprime positions a(n + k) = (k+1)*n; then at the next prime position a new subsequence begins. 4
 2, 3, 6, 5, 10, 7, 14, 21, 28, 11, 22, 13, 26, 39, 52, 17, 34, 19, 38, 57, 76, 23, 46, 69, 92, 115, 138, 29, 58, 31, 62, 93, 124, 155, 186, 37, 74, 111, 148, 41, 82, 43, 86, 129, 172, 47, 94, 141, 188, 235, 282, 53, 106, 159, 212, 265, 318, 59, 118, 61, 122, 183, 244 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 COMMENTS A064920(a(n)) = n. LINKS R. Zumkeller, Table of n, a(n) for n = 2..10000 FORMULA a(n) = A007917(n) * (A064722(n) + 1) EXAMPLE a(7) = A007917(7) * (A064722(7) + 1) = 7 * (0 + 1) = 7; a(8) = A007917(8) * (A064722(8) + 1) = 7 * (1 + 1) = 14; a(9) = A007917(9) * (A064722(9) + 1) = 7 * (2 + 1) = 21; a(10) = A007917(10) * (A064722(10) + 1) = 7 * (3 + 1) = 28; a(11) = 11. MATHEMATICA a[n_?PrimeQ] := n; a[n_] := NextPrime[n, -1]*(n - NextPrime[n, -1] + 1); Table[a[n], {n, 2, 64}] (* Jean-François Alcover, Sep 19 2011 *) Flatten[First[#]Range[Last[#]-First[#]]&/@Partition[Prime[Range[20]], 2, 1]] (* Harvey P. Dale, May 03 2012 *) PROG (PARI) { for (n=2, 10000, if (isprime(n), a=m=n; k=2, a=k*m; k++); write("b064924.txt", n, " ", a) ) } \\ Harry J. Smith, Sep 29 2009 (Haskell) import Data.List (genericTake) a064924 n = a064924_list !! (n-1) a064924_list = concat \$ zipWith (\p g -> genericTake g [p, 2 * p ..]) a000040_list \$ zipWith (-) (tail a000040_list) a000040_list -- Reinhard Zumkeller, Jul 05 2013 CROSSREFS Cf. A064920, A064923, A007917, A064722, A064919. Sequence in context: A338702 A064919 A064923 * A196330 A332462 A358137 Adjacent sequences: A064921 A064922 A064923 * A064925 A064926 A064927 KEYWORD nice,nonn,look AUTHOR Reinhard Zumkeller, Oct 14 2001 STATUS approved

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Last modified September 17 23:36 EDT 2024. Contains 375991 sequences. (Running on oeis4.)