Primes as they occur for the first time as factors of terms of A173426 = concatenation(1,2,...,n,n-1,...,1).

A260597

Primes as they occur for the first time as factors of terms of A173426 = concatenation(1,2,...,n,n-1,...,1).

Terms

    a(0) =11a(1) =3a(2) =37a(3) =101a(4) =41a(5) =271a(6) =7a(7) =13a(8) =239a(9) =4649a(10) =73a(11) =137a(12) =333667a(16) =1109a(17) =4729a(19) =571a(20) =3167a(21) =10723a(22) =439781a(24) =75401a(25) =687437a(26) =759077450603

External references