20735

Appears in sequences

• Heptagonal (or 7-gonal) pyramidal numbers: a(n) = n*(n+1)*(5*n-2)/6.at n=29A002413
• The larger of a betrothed pair.at n=7A003503
• Betrothed (or quasi-amicable) numbers.at n=15A005276
• a(n) = 12^n - 1.at n=4A024140
• Number of partitions satisfying 0 < cn(2,5) + cn(3,5).at n=37A039897
• a(n) in base 12 is a repdigit.at n=44A048336
• Positive numbers which are one less than a perfect square that is also another power.at n=15A062965
• a(n) = n^phi(n) - 1.at n=11A066916
• Nonprime solutions to k == -1 (mod phi(k+1)).at n=40A067930
• Numbers n such that sum of distinct primes dividing n is divisible by the largest prime dividing n. Also n is neither a prime, nor a true power of prime and n is squarefree. Squarefree solutions of A071140.at n=23A071141
• Numbers n such that (i) the sum of the distinct primes dividing n is divisible by the largest prime dividing n and (ii) n has exactly 4 distinct prime factors and (iii) n is squarefree.at n=9A071143
• Squarefree numbers k such that the largest prime factor of k is equal to the sum of the other prime factors of k.at n=22A071312
• Expansion of (1-x)^(-1)/(1-2*x+2*x^2-2*x^3).at n=21A077858
• Numbers k such that k divides tau(k) and k+1 divides tau(k+1), where tau(k)=A000594(k) is Ramanujan's tau function; i.e., k and k+1 are in A063938.at n=35A079334
• a(n) = Fibonacci(n+2)^2 - 1.at n=10A080097
• a(n) = F(4)*F(n)*F(n+1) + F(5)*F(n+1)^2 if n odd, a(n) = F(4)*F(n)*F(n+1) + F(5)*F(n+1)^2 - F(5) if n even, where F(n) is the n-th Fibonacci number (A000045).at n=9A080144
• Numbers whose set of base 12 digits is {0,B}, where B base 12 = 11 base 10.at n=15A097258
• Structured disdyakis dodecahedral numbers (vertex structure 9).at n=14A100161
• a(n)= 3*a(n-1) -3*a(n-3) +a(n-4), n>6.at n=13A107840
• Primitive elements of A065607.at n=16A120692