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Excess of n-th semiprime over previous prime.

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1, 1, 2, 3, 1, 2, 2, 3, 2, 3, 2, 3, 4, 1, 2, 3, 2, 4, 2, 4, 5, 1, 4, 2, 1, 4, 3, 2, 3, 4, 2, 4, 5, 6, 3, 2, 2, 5, 6, 8, 9, 10, 2, 2, 3, 2, 3, 4, 6, 7, 4, 1, 2, 4, 3, 2, 4, 5, 2, 4, 6, 1, 2, 3, 4, 6, 7, 10, 2, 3, 4, 6, 7, 8, 10, 3, 2, 4, 6, 8, 2, 3, 2, 5, 2, 4, 3, 1, 4, 6, 8, 2, 5, 6, 8, 9, 10, 12, 2, 1, 2, 4, 6 (list; graph; listen)

	OFFSET	`1,3`
	COMMENT	`a(n) = 1 iff n is in A077068. a(n) = 2 iff n is in A062721.`
	LINKS	`Robert G. Wilson, v, Table of n, a(n) for n=1..1000.`
	FORMULA	`a(n) = Min{A001358(n)-p for p<A001358(n) and p in A000040(k)}.`
	MATHEMATICA	`semiPrimeQ[n_] := Plus @@ Last /@ FactorInteger[n] == 2; lst1 = Select[ Range@ 325, semiPrimeQ@# &]; lst = Select[ Range@ 500, semiPrimeQ@# &]; lst - (NextPrime[ #, -1] & /@ lst) [From Robert G. Wilson v (rgwv(AT)rgwv.com), Mar 16 2009]`
	CROSSREFS	`Cf. A000040, A001358, A062721, A077068.` `Sequence in context: A036848 A128864 A106798 this_sequence A079087 A159956 A053839` `Adjacent sequences: A121881 A121882 A121883 this_sequence A121885 A121886 A121887`
	KEYWORD	`easy,nonn`
	AUTHOR	`Jonathan Vos Post (jvospost3(AT)gmail.com), Aug 31 2006`
	EXTENSIONS	`a(31)-a(103) from Robert G. Wilson v (rgwv(AT)rgwv.com), Mar 16 2009`

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Last modified November 30 13:13 EST 2009. Contains 167758 sequences.

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