id:A134099 - OEIS Search Results

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Odd numbers that are preceded by but not followed by primes.

+0
5

25, 33, 49, 55, 63, 75, 85, 91, 115, 133, 141, 153, 159, 169, 175, 183, 201, 213, 235, 243, 253, 259, 265, 273, 285, 295, 319, 333, 339, 355, 361, 369, 375, 385, 391, 403, 411, 423, 435, 445, 451, 469, 481, 493, 505, 511, 525, 543, 549, 559, 565, 573, 579 (list; graph; listen)

	OFFSET	`1,1`
	COMMENT	`Primes referred to in the example are found in A124582 - see A083370 and compare A124582`
	EXAMPLE	`a(1)=25 because it is an odd nonprime preceded by the prime 23 and followed by the nonprime odd 27`
	PROGRAM	`UBASIC: 10 'primes using counters 20 N=3:print "2 "; :print "3 "; :C=2 30 A=3:S=sqrt(N) 40 B=N\A 50 if B*A=N then 55 55 Q=N+2:R=N-2: if Q<>prmdiv(Q) and N<>prmdiv(N) and R=prmdiv(R) then print Q; N; R; "-"; :stop:else N=N+2:goto 30 60 A=A+2 70 if A<=sqrt(N) then 40:stop 81 C=C+1 100 N=N+2:goto 30`
	CROSSREFS	`Cf. A124582 A083370 A134100 A134101 A007510.` `Sequence in context: A050694 A107608 A131610 this_sequence A129074 A068411 A020160` `Adjacent sequences: A134096 A134097 A134098 this_sequence A134100 A134101 A134102`
	KEYWORD	`easy,nonn`
	AUTHOR	`Enoch Haga (Enokh(AT)comcast.net), Oct 08 2007`

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Last modified December 4 21:35 EST 2008. Contains 151309 sequences.

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