21109

Appears in sequences

• a(n) is the sum of squares of the first n positive integers congruent to 2 mod 3.at n=18A024394
• 4-white numbers: partition digits of n^4 into blocks of 4 starting at right; sum of these 4-digit numbers equals n.at n=13A037044
• a(n) = (1/9)*(-1+10^n)*(4*n+3).at n=3A095752
• a(n) = A169780(2^n).at n=8A169781
• Composite numbers n such that the distinct digits in n and the distinct digits in the proper divisors of n are the same.at n=15A237713
• Fundamental discriminants d uniquely characterizing all complex biquadratic fields Q(sqrt(-3),sqrt(d)) which have 3-class group of type (3,3) and second 3-class group isomorphic to either SmallGroup(2187,247)-#1;5 or SmallGroup(2187,247)-#1;9.at n=3A250242
• Numbers k such that the set of all the decimal digits of k is the same as the set of all the decimal digits of the proper divisors of k.at n=16A282755
• Number of partitions of n with rank a multiple of 3.at n=42A328988