21698

Appears in sequences

• Numbers n such that prime(k)*n+prime(k+1), for k=1,...,6 all are primes.at n=3A108110
• a(n) = A000043(n) - 3.at n=23A139480
• The Wiener index of a chain of n squares joined at vertices (i.e., joined like <><><>...<>; here <> is a square!).at n=18A143943
• Even indices of multidigit primes with digits in strictly increasing order.at n=33A155776
• Hypercomma numbers: n occurs in the sequence S[k+1]=S[k]+10*last_digit(S[k-1])+first_digit(S[k]) for each "legal" splitting n=concat(S[0],S[1]).at n=40A166508
• 3-comma numbers: n occurs in the sequence S[k+1]=S[k]+10*last_digit(S[k-1])+first_digit(S[k]) for three different splittings n=concat(S[0],S[1]).at n=24A166513
• Number of integer partitions of n whose parts have choosable sets of integer partitions.at n=48A387328