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 A053707 First differences of A025475, powers of a prime but not prime. 12
 3, 4, 1, 7, 9, 2, 5, 17, 15, 17, 40, 4, 3, 41, 74, 13, 33, 54, 18, 151, 17, 96, 104, 112, 120, 63, 307, 38, 312, 168, 199, 139, 10, 12, 192, 408, 316, 356, 240, 375, 393, 424, 128, 288, 912, 320, 298, 30, 1032, 271, 1217, 792, 408, 840, 432, 286, 602, 1872, 984, 504 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS In the graph of this sequence, the lowest curve corresponds to differences of squares of twin primes; the next-lowest curve is for squares of adjacent primes differing by 4, etc. - T. D. Noe, Aug 03 2007 LINKS T. D. Noe, Table of n, a(n) for n=1..10000 FORMULA a(n) = A025475(n+1) - A025475(n). EXAMPLE 2^0 = 1 is the first number that meets the definition of A025475, the next one is 2^2 = 4, hence a(1) = 4 - 1 = 3. a(3) = A025475(4) - A025475(3) = 9 - 8 = 1; a(11) = A025475(12) - A025475(11) = 121 - 81 = 40. MATHEMATICA Differences@ Join[{1}, Select[Range@ 16200, And[! PrimeQ@ #, PrimePowerQ@ #] &]] (* Michael De Vlieger, Jul 04 2016 *) PROG (PARI) {k=1; for(n=2, 16300, if(matsize(factor(n))[1]==1&&factor(n)[1, 2]>1, d=n-k; print1(d, ", "); k=n))} \\ Klaus Brockhaus, Sep 25 2003 CROSSREFS Cf. A025475. Sequence in context: A076446 A053289 A076412 * A075052 A111516 A210636 Adjacent sequences:  A053704 A053705 A053706 * A053708 A053709 A053710 KEYWORD nonn AUTHOR Labos Elemer, Feb 14 2000 EXTENSIONS Edited by Klaus Brockhaus, Sep 25 2003 STATUS approved

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Last modified August 10 13:12 EDT 2022. Contains 356039 sequences. (Running on oeis4.)