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 A146985 I call this sequence "symmetrical spooky primes" as two prime combinations are used in cryptography: f(n)=If[n==0,1,Prime[n]]; t(n,m)=f(n-m)*f(n). 1
 1, 2, 2, 3, 4, 3, 5, 6, 6, 5, 7, 10, 9, 10, 7, 11, 14, 15, 15, 14, 11, 13, 22, 21, 25, 21, 22, 13, 17, 26, 33, 35, 35, 33, 26, 17, 19, 34, 39, 55, 49, 55, 39, 34, 19, 23, 38, 51, 65, 77, 77, 65, 51, 38, 23, 29, 46, 57, 85, 91, 121, 91, 85, 57, 46, 29 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Row sums are:{1, 4, 10, 22, 43, 80, 137, 222, 343, 508, 737}. The sequence to Floor[n/2] is a way to get all the combinations of primes with one less than the other. LINKS FORMULA f(n)=If[n==0,1,Prime[n]]; t(n,m)=f(n-m)*f(n). EXAMPLE {1}, {2, 2}, {3, 4, 3}, {5, 6, 6, 5}, {7, 10, 9, 10, 7}, {11, 14, 15, 15, 14, 11}, {13, 22, 21, 25, 21, 22, 13}, {17, 26, 33, 35, 35, 33, 26, 17}, {19, 34, 39, 55, 49, 55, 39, 34, 19}, {23, 38, 51, 65, 77, 77, 65, 51, 38, 23}, {29, 46, 57, 85, 91, 121, 91, 85, 57, 46, 29} MATHEMATICA Clear[f, t, n, m]; f[n_] := If[n == 0, 1, Prime[n]]; t[n_, m_] = f[n - m]*f[m]; Table[t[n, m], {n, 0, 10}, {m, 0, n}]; Flatten[%] CROSSREFS Sequence in context: A290735 A165634 A128282 * A132993 A106408 A143061 Adjacent sequences:  A146982 A146983 A146984 * A146986 A146987 A146988 KEYWORD easy,nonn AUTHOR Roger L. Bagula, Nov 04 2008 STATUS approved

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Last modified May 15 12:37 EDT 2021. Contains 343920 sequences. (Running on oeis4.)