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 A075560 a(1) = 1, a(n) is the smallest number greater than the previous term that cannot be obtained as the sum of products of any group of earlier terms. 0
 1, 2, 4, 10, 22, 50, 106, 230, 480, 1054, 2656, 6782, 17254 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Next term is > 37000. - David Wasserman, Jan 20 2005 LINKS Table of n, a(n) for n=1..13. EXAMPLE a(5) = 22, as using 1, 2, 4 and 10 the following numbers can be generated: 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 24, 25, 40, 41, 42, 43, 80 and 81. E.g., 19 = 10 + 2*4 + 1. PROG (PARI) canMake(n, v) = local(l, newV, m, c, count, mm, x); if (n < 0, return(0)); if (n == 0, return(1)); l = length(v); if (l == 0, return(0)); newV = vector(l - 1, i, v[i]); if (canMake(n, newV), return(1)); m = v[l]; c = l - 1; if (canMake(n - m, newV), return(1)); while (c && v[c]*m > n, c--); for (i = 1, 2^c - 1, count = 0; mm = m; x = i; for (j = 1, c, if (x%2, mm *= v[j], count++; newV[count] = v[j]); x \= 2); for (j = c + 1, l - 1, newV[j - c + count] = v[j]); if (canMake (n - mm, vector(l - 1 - c + count, q, newV[q])), return(1))); 0; v = [2]; n = 4; while (1, if (canMake(n, v), n += 2, l = length(v); newV = vector(l + 1); for (i = 1, l, newV[i] = v[i]); newV[l + 1] = n; v = newV; print(n); n = 2*n + 2)); \\ David Wasserman, Jan 20 2005 CROSSREFS Sequence in context: A260916 A192627 A275445 * A078040 A240041 A164990 Adjacent sequences: A075557 A075558 A075559 * A075561 A075562 A075563 KEYWORD nonn,hard,more AUTHOR Amarnath Murthy, Sep 24 2002 EXTENSIONS Corrected and extended by David Wasserman, Jan 20 2005 Offset corrected by Mohammed Yaseen, Jul 21 2023 STATUS approved

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Last modified February 21 09:51 EST 2024. Contains 370228 sequences. (Running on oeis4.)