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A160690
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a(1)=1. a(n) = the smallest integer > a(n-1) such that d(a(n)) = d(a(n) - a(n-1)), where d(m) = the number of divisors of m.
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5
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1, 3, 5, 7, 15, 17, 19, 27, 29, 31, 39, 41, 43, 51, 53, 74, 79, 85, 91, 106, 109, 115, 123, 129, 131, 141, 153, 159, 171, 173, 183, 205, 213, 219, 253, 259, 265, 287, 295, 301, 309, 311, 313, 319, 327, 335, 337, 343, 358, 389, 395, 397, 403, 411, 417, 419, 421
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OFFSET
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1,2
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COMMENTS
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LINKS
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MATHEMATICA
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a[1] = 1; a[n_] := a[n] = (For[m = a[n - 1] + 1, DivisorSigma[0, m] != DivisorSigma[0, m - a[n - 1]], m++]; m); Table[a[n], {n, 57}] (* Farideh Firoozbakht, May 28 2009 *)
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PROG
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(PARI) lista(nn) = {k = 1; print1(k, ", "); last = k; for (n=2, nn, k = last+1; while(numdiv(k) != numdiv(k - last), k++); print1(k, ", "); s += k; last = k; ); } \\ Michel Marcus, Sep 05 2017
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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