

A185191


a(n) = 2^n  second largest prime less than 2^n.


1



2, 3, 5, 3, 5, 15, 15, 9, 5, 19, 5, 13, 15, 49, 17, 9, 11, 19, 5, 19, 17, 21, 17, 49, 27, 79, 89, 33, 41, 19, 17, 25, 77, 49, 17, 31, 87, 19, 167, 31, 17, 67, 117, 69, 57, 127, 65, 111, 35, 139, 143, 145, 53, 67, 27, 25, 57, 99, 107, 31, 87, 165, 83
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OFFSET

2,1


REFERENCES

D. E. Knuth, The Art of Computer Programming Second Edition. Vol. 2, Seminumerical Algorithms. Chapter 4.5.4 Factoring into Primes, Table 1, Page 390, AddisonWesley, Reading, MA, 1981.


LINKS



FORMULA

a(n) = 2^n  precprime(precprime(2^n)1)


EXAMPLE

a(2)=2 because precprime(4)=3, and precprime(2)=2.


MATHEMATICA

Table[2^n  NextPrime[2^n, 2], {n, 2, 64}] (* T. D. Noe, Jan 24 2012 *)


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



