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A108245 If n-th prime is 4m-1, then a(n) = 4m+1. If n-th prime is 4m+1, then a(n) = 4m-1. +0
2
5, 3, 9, 13, 11, 15, 21, 25, 27, 33, 35, 39, 45, 49, 51, 61, 59, 69, 73, 71, 81, 85, 87, 95, 99, 105, 109, 107, 111, 129, 133, 135, 141, 147, 153, 155, 165, 169, 171, 181, 179, 193, 191, 195, 201, 213, 225, 229, 227, 231, 241, 239, 253, 255, 265, 267, 273, 275, 279 (list; graph; listen)
OFFSET

2,1

LINKS

Leroy Quet, Home Page (listed in lieu of email address)

EXAMPLE

11, the 5th prime, is of the form 4m-1, so a(5) = 4m+1 = 13.

MAPLE

a:=proc(n) if ithprime(n) mod 4 = 3 then ithprime(n)+2 else ithprime(n)-2 fi end: seq(a(n), n=2..75); (Deutsch)

CROSSREFS

Cf. A107323.

Sequence in context: A019955 A075693 A082454 this_sequence A141620 A049829 A137613

Adjacent sequences: A108242 A108243 A108244 this_sequence A108246 A108247 A108248

KEYWORD

nonn

AUTHOR

Leroy Quet Jun 17 2005

EXTENSIONS

More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Jun 19 2005

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Last modified November 29 12:46 EST 2009. Contains 167659 sequences.


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