login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A262182 Prime numbers of the form (n*(n+1)/2)^2 + 1. 1
2, 37, 101, 1297, 4357, 14401, 44101, 90001, 164837, 246017, 608401, 894917, 1382977, 4326401, 8122501, 8561477, 9985601, 10497601, 38638657, 46049797, 52707601, 84272401, 121572677, 146168101, 165894401, 201526417, 259532101, 289680401, 404010001, 428738437 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Sum_{n>=1} 1/a(n) = 0.538046187...

LINKS

Chai Wah Wu, Table of n, a(n) for n = 1..5231

FORMULA

a(n) = A154323(A217755(n)). - Michel Marcus, Oct 02 2015

a(n) = ((A217755(n)^2 + A217755(n))/2)^2 + 1. - Jean C. Lambry, Oct 07 2015

PROG

(Python 2.7)

def prime (n):

    if (n == 1): return True

    d = n + 1

    c = n - 1

    while (c > 0 and d%c != 0):

        d = d + n

        c = c - 1

    if (c == 1):

        return True

    else:

        return False

n = 1

i = 1

while (i <= 500):

    target = i * (i + 1) / 2

    if(prime(target) == True):

        print n, target*target+1

        n = n + 1

    i = i + 1

\\ Jean C. Lambry, Oct 06 2015

(PARI) for(n=1, 1e3, if(isprime(k = (n*(n+1)/2)^2+1), print1(k", "))) \\ Altug Alkan, Oct 02 2015

CROSSREFS

Cf. A154323, A217755.

Sequence in context: A041161 A106947 A258896 * A142077 A107182 A134596

Adjacent sequences:  A262179 A262180 A262181 * A262183 A262184 A262185

KEYWORD

nonn

AUTHOR

Jean C. Lambry, Oct 02 2015

EXTENSIONS

More terms from Altug Alkan, Oct 02 2015

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 25 22:28 EDT 2019. Contains 321477 sequences. (Running on oeis4.)