A177966 - OEIS

A177966

Indices m for which A177961(m) = 2 + m.

2, 5, 8, 11, 12, 14, 20, 23, 26, 27, 29, 35, 41, 42, 44, 50, 53, 56, 57, 65, 68, 74, 83, 86, 87, 89, 95, 98, 113, 116, 117, 119, 125, 128, 131, 132, 134, 140, 146, 147, 155, 158, 173, 176, 177, 179, 191, 192, 194, 200, 209, 215, 221, 222, 224, 230, 233, 239, 245, 251, 252, 254

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

All m for which 2*m+1 is in A003627 are in the sequence:

This concerns m=2, 5, 8, 11, 14, 20, 23, 26, 29, 35,...

Union of (A003627-1)/2 and (A132235+1)/2. - Robert Israel, Jul 31 2015

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

MAPLE

A090368 := proc(n) A020639(2*n-1) ; end proc:

A177961 := proc(n) (A090368(n)+A090368(n+1)) /2 ; end proc:

isA177966 := proc(n) A177961(m) = m+2 ; end proc:

for m from 1 to 800 do if isA177966(m) then printf("%d, ", m) ; end if; end do:

# R. J. Mathar, Oct 25 2010

N:= 1000: # to get all terms <= N

A1:= map(t -> (t-1)/2, select(isprime, {seq(6*i-1, i=1..(N+1)/3)})):

A2:= map(t -> (t+1)/2, select(isprime, {seq(23+30*i, i=0..(N-12)/15)})):

sort(convert(A1 union A2, list));

# Robert Israel, Jul 31 2015

MATHEMATICA

M = 1000; (* to get all terms <= M *)

A1 = (Select[Table[6 i - 1, {i, 1, (M + 1)/3}], PrimeQ] - 1)/2;

A2 = (Select[Table[23 + 30 i, {i, 0, (M - 12)/15}], PrimeQ] + 1)/2;

Union[A1, A2] (* Jean-François Alcover, Jul 17 2020, after Robert Israel *)

CROSSREFS

Cf. A003627, A132235, A177961, A177964, A177965.

Sequence in context: A124934 A125217 A277574 * A083422 A187581 A167409

Adjacent sequences: A177963 A177964 A177965 * A177967 A177968 A177969

KEYWORD

nonn

AUTHOR

Vladimir Shevelev, May 16 2010

EXTENSIONS

Corrected (11, 23, 27, etc. inserted) and extended by R. J. Mathar, Oct 25 2010

STATUS

approved