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A140388 Composites of the form ((3*x*y-y-6)/(3*x+1), where x=composite and y=prime. 0


%S 1,49,55,85,145,175,187,235,247,259,265,289,343,355,385,415,427,445,

%T 475,505,517,553,559,565,583,589,595,655,679,697,715,793,805,835,925,

%U 943,949,979,1015,1027,1045,1057,1099,1105,1147,1159,1183,1219,1225,1255

%N Composites of the form ((3*x*y-y-6)/(3*x+1), where x=composite and y=prime.

%C x=c(i)=i-th composite and y=p(j)=j-th prime.

%e If x=1 and y=5, then ((3*1*5-5-6)/(3*1+1)=4/4=1=a(1).

%e If x=9 and y=53, then ((3*9*53-53-6)/(3*9+1)=1372/28=49=a(2).

%e If x=10 and y=59, then ((3*10*59-59-6)/(3*10+1)=1705/31=55=a(3).

%e If x=15 and y=89, then ((3*15*89-89-6)/(3*15+1)=3910/46=85=a(4).

%e If x=25 and y=149, then ((3*25*149-149-6)/(3*25+1)=11020/76=145=a(5).

%e If x=30 and y=179, then ((3*30*179-179-6)/(3*30+1)=15925/91=175=a(6),

%e etc.

%Y Cf. A002808, A000040.

%K nonn

%O 1,2

%A _Juri-Stepan Gerasimov_, Aug 28 2008

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Last modified August 22 11:34 EDT 2019. Contains 326176 sequences. (Running on oeis4.)