Let a(0)=1. Then a(n) = sums of consecutive strings of positive integers of length 3*n, starting with the integer 2.

A289721

Let a(0)=1. Then a(n) = sums of consecutive strings of positive integers of length 3*n, starting with the integer 2.

Terms

    a(0) =1a(1) =9a(2) =45a(3) =135a(4) =306a(5) =585a(6) =999a(7) =1575a(8) =2340a(9) =3321a(10) =4545a(11) =6039a(12) =7830a(13) =9945a(14) =12411a(15) =15255a(16) =18504a(17) =22185a(18) =26325a(19) =30951a(20) =36090a(21) =41769a(22) =48015a(23) =54855a(24) =62316a(25) =70425a(26) =79209a(27) =88695a(28) =98910a(29) =109881

External references