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A085766
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Smallest m such that n divides the tetrahedral number A000292(m+1).
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0
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1, 1, 6, 1, 2, 6, 4, 5, 24, 2, 8, 6, 10, 5, 7, 13, 14, 25, 16, 3, 6, 9, 20, 7, 22, 10, 78, 5, 26, 7, 28, 29, 8, 14, 4, 25, 34, 17, 24, 7, 38, 6, 40, 9, 24, 21, 44, 15, 46, 22, 15, 11, 50, 78, 8, 5, 16, 26, 56, 7, 58, 29, 25, 61, 12, 42, 64, 14, 43, 13, 68, 53, 70, 34, 24, 17, 19, 25, 76, 13
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OFFSET
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1,3
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LINKS
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EXAMPLE
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Let te(m)=(m+1)(m+2)(m+3)/6. Then te(1)=4, te(2)=10, te(3)=20, te(4)=35, te(5)=56 and te(6)=84. te(6) is the first tetrahedral number divisible by 3, hence a(3)=6.
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PROG
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(PARI) te(n)=(n+1)*(n+2)*(n+3)/6 for (n=1, 50, c=1; while (te(c)%n!=0, c++); print1(c", "))
(PARI) first(n) = {my(res = vector(n), todo = n); res[1] = 1; todo--; for(i = 1, oo, t = binomial(i + 2, 3); d = divisors(t); for(j = 1, #d, if(d[j] <= n && res[d[j]] == 0, res[d[j]] = i - 1; todo--; if(todo <= 0, return(res); ) ) ) ) } \\ David A. Corneth, Mar 22 2021
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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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