21022

Appears in sequences

• Coordination sequence for Cr3Si, Cr position.at n=37A009928
• a(n) = 1 - (7/6)*n + (2/3)*n^3 + (1/2)*n^4.at n=14A046998
• Numbers which contain exactly the same digits (with the correct multiplicity) in 3 different smaller bases.at n=35A059828
• Heptagonal numbers for which the sum of the digits is also a heptagonal number.at n=23A117650
• Heptagonal numbers for which the digital root is also a heptagonal number.at n=42A117663
• Number of non-isomorphic maximal independent sets of the n-cycle graph having no symmetry axis.at n=51A127686
• Numbers which are both heptagonal and centered heptagonal.at n=2A128919
• Concatenation of first n numbers of the decimal expansion of imaginary part of 2nd nontrivial zero of Riemann zeta function.at n=4A131584
• Heptagonal numbers A000566 which are the sum of two other heptagonal numbers > 0.at n=10A133251
• Least k such that k*(2^p-1)*(k*(2^p-1)-1)-1 is prime, where 2^p-1 runs through the Mersenne primes.at n=24A137906
• E.g.f. satisfies: A(x) = Sum_{n>=0} x^n/n! * A(x)^(n(n-1)/2).at n=7A155804
• Multiples of 23 whose digit reversal - 1 is also a multiple of 23.at n=36A166400
• Numbers 3*n + 2 written in base 3.at n=65A190642
• Number of nondecreasing -2..2 vectors of length n whose dot product with some nonincreasing -2..2 vector equals n.at n=29A226393
• Not necessarily palindromic primes of which initial and terminal digits are identical, as written in base 3.at n=19A231278
• Numbers n such that n^9+9 and n^9-9 are prime.at n=17A239505
• Sum of primes between 100*n and 100*n + 99.at n=17A276355
• Number of permutations of [n] avoiding {1324, 2143, 3421}.at n=11A294700
• Positive integers that have exactly ten representations of the form 1 + p1 * (1 + p2* ... * (1 + p_j)...), where [p1, ..., p_j] is a (possibly empty) list of distinct primes.at n=17A317400
• a(n) = [x^n] Product_{k>=1} (1 + x^k)^binomial(k+n-1,n-1).at n=6A344098