21139

Properties

Appears in sequences

• Sequence A001033 gives the numbers n such that the sum of the squares of n consecutive odd numbers x^2 + (x+2)^2 + ... +(x+2n-2)^2 = k^2 for some integer k. For each n, this sequence gives the least value of x.at n=44A056131
• The sum of the sequence starting with prime(n) and having prime sum defined in A071194, or -1 if no such sequence exists.at n=48A071196
• a(n) = n^3 - n^2 - n - 1.at n=28A083074
• Primes of the form p = prime(k) = (prime(k+3)+prime(k-1))/2.at n=20A126238
• Primes of the form k^3-k^2-k-1.at n=6A162295
• Primes p that p//13 and p//31 are consecutive primes.at n=30A176601
• Primes p such that p plus or minus the sum of the fourth powers of its digits is a prime in both cases.at n=33A179595
• Primes with eight embedded primes.at n=10A179916
• 0-sequence of reduction of the upper Wythoff sequence by x^2 -> x+1.at n=14A192302
• Numbers appearing in A214208 excluding powers 2^i with i>0.at n=14A214209
• Denominators of the continued fraction convergents of log_10(11).at n=9A215756
• Numbers k such that the first k digits of the string kkkk... correspond to a prime number.at n=5A216449
• Largest prime that can be obtained from n by successively appending digits to the right with the constraint that each of the numbers obtained that way must be prime; a(n)=0 if there is no such prime at all.at n=20A232129
• Primes p where q = p + 4 is also prime and rad((p+1)(p+2)(p+3)) < pq, where rad(k) is the largest squarefree number dividing k.at n=15A268350
• Smallest prime p such that the Diophantine equation x + y + z = p with x*y*z = k^3 (0 < x <= y <= z) has exactly n solutions.at n=36A290401
• Number of unoriented series-parallel networks with integer valued elements summing to n.at n=8A339284
• Primes p such that A001414(p+q) is the square of a prime, where q is the next prime after p.at n=42A342830
• Primes p such that the sum of A001414(k) for k strictly between p and the following prime is a proper prime power (a term of A246547).at n=45A343123
• Discriminants of imaginary quadratic fields with class number 37 (negated).at n=18A351675
• a(1) = 1, a(2) = 2. For n > 2, a(n) is the least novel power of the greatest prime divisor of a(n-2) + a(n-1).at n=34A359874