21191

Properties

Appears in sequences

• Discriminants of quintic fields with 2 complex conjugates (negated).at n=35A023684
• a(n) = Sum_{k=0..n} (k+1) * A026780(n, k).at n=10A027251
• Primes p whose reciprocal has period (p-1)/10.at n=28A056215
• Decimal encoding of the prime factorization of n: concatenation of prime factors and exponents.at n=36A067599
• a(1) = 11 by convention; for n > 1, if n = p^a*q^b... then a(n) = concatenate(p,a,q,b,...).at n=37A068633
• Primes congruent to 24 mod 61.at n=37A142822
• Primes p such that continued fraction of (1 + sqrt(p))/2 has period 8; primes in A146333.at n=15A146353
• a(n) = 49*n^2 - 20*n + 2.at n=20A157373
• Upper Beatty array of sqrt(2).at n=36A182638
• Primes of the form 2*n^2 + 74*n + 35.at n=10A217500
• Construct sequences P,Q,R by the rules: Q = first differences of P, R = second differences of P, P starts with 1,3,9, Q starts with 2,6, R starts with 4; at each stage the smallest number not yet present in P,Q,R is appended to R. Sequence gives P.at n=44A225385
• Number of n X 2 0,1 arrays indicating 2 X 2 subblocks of some larger (n+1) X 3 binary array having an odd sum, with rows and columns of the latter in lexicographically nondecreasing order.at n=12A227675
• Primes in A065387 in the order of their appearance.at n=32A229264
• Primes p such that the norm of the quadratic-field analog of Mersenne numbers M_{p,alpha} = (alpha^p - 1)/(alpha - 1), with alpha = 2 + sqrt(2), is a rational prime.at n=11A323697
• Twin primes p such that the absolute difference of p and the reverse of its twin is a twin prime.at n=37A342216
• Lesser of twin primes p,p+2 such that the absolute difference of p and the reverse of p+2 is a twin prime and the absolute difference of p+2 and the reverse of p is a twin prime.at n=8A342299
• Primes having only {1, 2, 9} as digits.at n=35A385776
• Prime numbersat n=2383