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A061286
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Smallest integer for which the number of divisors is the n-th prime.
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25
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2, 4, 16, 64, 1024, 4096, 65536, 262144, 4194304, 268435456, 1073741824, 68719476736, 1099511627776, 4398046511104, 70368744177664, 4503599627370496, 288230376151711744, 1152921504606846976
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Seems to be the same as "Even numbers with prime number of divisors" - Jason Earls (zevi_35711(AT)yahoo.com), Jul 04 2001
Except for the first term, smallest number == 1 (mod prime(n)) having n divisors (by Fermat's little theorem). - Amarnath Murthy and Meenakshi Srikanth (amarnath_murthy(AT)yahoo.com), Jun 20 2003
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FORMULA
| a(n) = 2^[p(n)-1] = Min{k| A000005(k) = prime} = 2^A006093(n).
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PROG
| (PARI) forstep(n=2, 100000000, 2, x=numdiv(n); if(isprime(x), print(n)))
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CROSSREFS
| Cf. A000040, A000005, A005179, A003680, A061283, A061286, A006093, A005097, A006254.
Cf. A196202.
Sequence in context: A154001 A154004 A060656 * A019279 A061652 A162119
Adjacent sequences: A061283 A061284 A061285 * A061287 A061288 A061289
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), May 22 2001
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