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A037176 Numbers n such that us(n) = number of primes <= n, where usigma(n) = sum of unitary divisors of n (A034448), us(n) is usigma(n)-n. 0
1, 2, 56, 80, 85, 2527, 2569, 2723, 2807, 7864, 7976, 22941, 113488, 174449, 461403, 1302379, 8513821, 14348051, 70110091, 70111621, 70112369, 249046528 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..22.

PROG

(PARI) us(n) = sumdiv(n, d, if(gcd(d, n/d)==1, d)); f(n)=s=0; for(x=1, n, if(isprime(x), s++)); s; for(n=1, 10^6, if(us(n)-n==f(n), print(n)))

CROSSREFS

Sequence in context: A210928 A210932 A278842 * A045819 A193830 A196539

Adjacent sequences:  A037173 A037174 A037175 * A037177 A037178 A037179

KEYWORD

nonn

AUTHOR

Naohiro Nomoto

EXTENSIONS

a(12) from Jason Earls (zevi_35711(AT)yahoo.com), Sep 06 2001

a(13) - a(15) from Nathaniel Johnston, Apr 29 2011

a(16)-a(22) from Donovan Johnson, Jul 24 2012

STATUS

approved

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Last modified December 5 15:24 EST 2016. Contains 278770 sequences.