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A264024 a(n) = gcd(phi(k), k-1) / lambda(k), where k is n-th Carmichael number A002997(n) and lambda(k) = A002322(k). 2
1, 1, 12, 2, 1, 1, 9, 1, 4, 1, 6, 18, 1, 1, 1, 2, 1, 1, 1, 2, 12, 1, 1, 1, 1, 3, 3, 3, 50, 1, 18, 2, 1, 2, 1, 2, 5, 36, 1, 1, 2, 3, 4, 3, 3, 2, 3, 1, 1, 3, 3, 2, 4, 2, 5, 1, 4, 4, 4, 1, 1, 3, 40, 28, 1, 2, 4, 2, 4, 1, 2, 1, 2, 1, 33, 5, 50, 64, 1, 1, 3, 2, 1, 1, 12, 3, 1, 12, 1, 1, 1, 24, 1, 3, 128, 1, 6, 8, 5, 20, 3, 2, 2, 6, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..105.

FORMULA

a(n) = A049559(k)/A002322(k), where k = A002997(n).

MATHEMATICA

t = Cases[Range[1, 16 (10^6), 2], n_ /; Mod[n, CarmichaelLambda@ n] == 1 && ! PrimeQ@ n]; Table[GCD[EulerPhi@ t[[n]], t[[n]] - 1]/CarmichaelLambda@ t[[n]], {n, 105}] (* Michael De Vlieger, Nov 03 2015, after Artur Jasinski at A002997: alternatively use A002997 data for t *)

PROG

(PARI) t(n)=my(f=factor(n)); for(i=1, #f[, 1], if(f[i, 2]>1||(n-1)%(f[i, 1]-1), return(0))); 1;

is(n)=n%2 && !isprime(n) && t(n) && n>1;

c(n)=gcd(eulerphi(n), n-1)/lcm(znstar(n)[2]);

for(n=1, 1e7, if(is(n), print1(c(n)", "))) \\ Altug Alkan, Nov 01 2015

CROSSREFS

Cf. A002322, A002997, A049559, A174590, A264012.

Sequence in context: A232627 A222582 A260621 * A010204 A124607 A177429

Adjacent sequences:  A264021 A264022 A264023 * A264025 A264026 A264027

KEYWORD

nonn

AUTHOR

Thomas Ordowski, Nov 01 2015

EXTENSIONS

More terms from Altug Alkan, Nov 01 2015

STATUS

approved

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Last modified August 1 12:59 EDT 2021. Contains 346391 sequences. (Running on oeis4.)