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A349867
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Generalized multiplicative Euler phi function of order 2 (see El Hindi et al. link).
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0
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1, 1, 1, 1, 2, 1, 2, 1, 2, 2, 4, 1, 4, 2, 2, 8, 8, 2, 6, 2, 2, 4, 10, 1, 8, 4, 6, 2, 12, 2, 8, 16, 4, 8, 4, 2, 12, 6, 4, 2, 16, 2, 12, 4, 4, 10, 22, 8, 12, 8, 8, 4, 24, 6, 8, 2, 6, 12, 28, 2, 16, 8, 4, 32, 8, 4, 20, 8, 10, 4, 24, 2, 24, 12, 8, 6, 8, 4, 24, 16
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OFFSET
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1,5
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LINKS
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PROG
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(PARI) phig(n, k) = {my(f=factor(n)); if (k==1, return(eulerphi(f))); for (j=1, #f~, my(p=f[j, 1], alfa=f[j, 2]); if (p % 2, f[j, 1] = if (alfa < k, phig(p-1, k-1)*prod(i=k-alfa+1, k-1, phig(p, i)), phig(p-1, k-1)*p^(alfa-k)*prod(i=1, k-1, phig(p, i))), f[j, 1] = if (alfa < 2*k, 1, 2^(alfa-1)); ); f[j, 2] = 1; ); factorback(f); }
a(n) = phig(n, 2);
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CROSSREFS
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KEYWORD
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nonn,mult
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AUTHOR
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STATUS
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approved
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