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A305726
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Totients t the solutions of which cannot be divided by a prime to yield the solutions of a totient < t.
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0
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1, 2, 4, 6, 8, 12, 16, 18, 20, 24, 32, 36, 40, 42, 48, 54, 60, 64, 72, 80, 84, 88, 96, 100, 108, 112, 120, 128, 132, 144, 156, 160, 162, 168, 176, 180, 192, 200, 216, 220, 224, 232, 240, 252, 256, 264, 272, 276, 280, 288, 294, 300, 312, 320, 324, 336, 342, 348, 352, 360, 384, 396, 400
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OFFSET
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1,2
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COMMENTS
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This sequence is the complement of A303746.
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LINKS
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EXAMPLE
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1 is a term because there is no prime that divides the solutions of phi(x) = 1 (1 and 2).
2 is a term because there is no prime that divides the solutions of phi(x) = 2 (3, 4, and 6).
10 is not a term because 11 divides solutions of phi(x) = 10 (11 and 22) yielding 1 and 2 the solutions of phi(x) = 1.
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PROG
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(PARI) isok(n) = {if (istotient(n), v = invphi(n); g = gcd(v); if (g == 1, return (1)); f = factor(g); for (k=1, #f~, vv = v/f[k, 1]; nt = eulerphi(vv[1]); if (vv == invphi(nt), return(0)); ); return (1); ); } \\ Michel Marcus, Jul 25 2018
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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