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A229322 Composite squarefree numbers n such that p + tau(n) divides n + phi(n), where p are the prime factors of n, tau(n) = A000005(n) and phi(n) = A000010(n). 2
72285, 82218, 1612671, 52371129, 511130199, 2111850465, 4789685289, 8884216243, 8916435021, 9863075721, 15364177629, 28243714821, 99459827349 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
a(15) > 10^11. - Giovanni Resta, Sep 20 2013
Subsequence of A120944.
LINKS
EXAMPLE
Prime factors of 82218 are 2, 3, 71, 193 and tau(82218) = 16, phi(82218) = 26680. 82218 + 26680 = 109098 and 109098 / (2 + 16) = 6061, 109098 / (3 + 16) = 5742, 109098 / (71 + 16) = 1254, 109098 / (193 + 16) = 522.
MAPLE
with (numtheory); P:=proc(q) global a, b, c, i, ok, p, n;
for n from 2 to q do if not isprime(n) then a:=ifactors(n)[2]; ok:=1;
for i from 1 to nops(a) do if a[i][2]>1 then ok:=0; break;
else if not type((n+phi(n))/(a[i][1]+tau(n)), integer) then ok:=0; break; fi; fi; od; if ok=1 then print(n); fi; fi; od; end: P(6*10^9);
CROSSREFS
Sequence in context: A254911 A254904 A257206 * A269320 A126658 A251340
KEYWORD
nonn
AUTHOR
Paolo P. Lava, Sep 20 2013
EXTENSIONS
a(4)-a(14) from Giovanni Resta, Sep 20 2013
First term deleted by Paolo P. Lava, Sep 23 2013
STATUS
approved

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Last modified March 29 09:59 EDT 2024. Contains 371268 sequences. (Running on oeis4.)